Call me a mad woman, but I read through Wendy's entire quotes late and wrote down every single time she mentions Abigail. (or just says 'sister'.) So now I'm going to share them with you, and provide my thoughts on some of the quotes. (Please note that because Wendy's quote page isn't quite complete, I may have missed one of two of these quotes.)
Cork candle hat- "only Abigail can light up my life."
midnight (on)- " abigail would have thought this was...pretty..."
Bundling wrap- "Abigail always helped me tie the bow."
bird whistle- " do you enjoy the wistful sound of bird song, Abigail? "
Whirly can- "when I am still, it is as lifeless as Abigail."
fish farm (1 fish) - "look, Abby. We have a visitor."
fish farm (2 fish)- "Abby...there's more now..."
potter's wheel(marble or cut stone placed.)- "Abigail...you be death, I'll be the sculptor..."
seaworthy (SW world.)- "Like my beloved sister, I can never return."
wardrobe- "it reminds me of a story I used to read with Abigail."
moondial (generic)- "Does it reflect from the other side too, Abigail?"
raincoat- "I liked jumping in puddles with Abigail."
thulecite crown- "Abigail would've loved this crown."
raft- "maybe if I ride this upon the waves I shall be joined with my sister."
the flying pig arcane shop- "can any of this magic bring back abigail?"
Orange wallpaper and purple wallpaper - "boring. Like life without abigail."
villa kit- "my home is with Abigail."
map scroll (empty)- "blank as abigail now."
honey crystals - "not as sweet as abigail."
ghost decoration - "it reminds me of abigail. I'll hang it some where." ( me and my dark mind:"hmmMMMmm what do you mean by hang? ")
Bats coming out of tree- "did you see that, Abigail?"
gift wrap - "Abby... How do I make the ribbon curly?"
festive bauble- "do you like this one, Abigail?" ( I might have spelled 'bauble' wrong...)
Holiday cheer- "makes me think of holidays with abigail."
can't play game (area not empty)- "help me clean up Abigail."
scorpeon - "Abigail will defend me."
gnaw worshipper (2)- "Abigail needs a statue." ( uhhh okkkiii wendy is a cultist... But now I want to draw an Abigail statue... And use iridescent gems for eyes...)
Stone pillar- "a monument. But not to Abigail."
small street light- "the only light in my light is abigail." ( on the wiki page it said 'light in my light' but I'm not sure if it's meant to be 'light in my life' or not)
Syrup- "not as sweet as Abigail."
Sapphire medallion - "money will not bring back Abigail."
tidal pool- "when I gaze into this limpid pool I dream I can see Abigail." ( idk what limpid means...)
mandrake hill- "Abigail lives in the ground too." ( uhhh well I guess she's technically correct...this is one of her darker quotes.)
Celestial orb- "it's pallor reminds me of Abigail." ( to the people who don't know, pallor means a pale, unhealthy appearance.)
Celestial alter idol- "Abby and I will help out you back together."
Honey chest- "still not as sweet as Abigail."
pirate ghost- "a future friend of Abigail's?"
ancient spirit - "do you know my sister Abigail?" ( I mean, both pigs and Abigail dislike Webber...)
Bandit stash map- "Abigail is the most valuable buried treasure." ( this quote is up beside her quotes for rope and corks, for being very dark. Wendy is like, 10 years old btw.)
Collector- "your curiosities are nothing compared to my Abigail." ( I read this as: "b*tch I talk to ghosts your stuff isn't that impressive." )
Professor - "you'll be seeing Abigail soon." ( that's one way to tell people that they're old...)
Down feather - "plucked like Abigail was from me."
large iron hulk- "Like Abigail, it has been resurrected from a deep sleep." ( she sure has a lot of synonyms for death...)
Toadstool and misery Toadstool (enraged)- "I think I'll be reunited with Abigail soon."
Abigail- "that's my twin sister, Abigail." ( I know that this is pretty obvious.)
Wilson (reviver)- "Abigail likes you, %s..." (Sorry if I'm spelling reviver wrong.)
willow (reviver)- "Abigail likes you, %s. Do you like her?"
willow (ghost)- "say hi to Abigail while I go get you a heart, %s."
Wolfgang (reviver)- "don't be scared, %s. Abigail just wants to be friends."
wendy (reviver)- "I hope Abigail doesn't like you more than me..."
wx-78 (reviver)- "Abigail likes you, %s." ( I like to imagine that wx-78 just one day telling Abby while wendy wasn't looking: "COME HELP ME KILL OFF AND ENSLAVE THE FLESHLINGS, UNDEAD CHILD." )
Wickerbottom (reviver)- "Abigail likes you, Ms. %s."
Woodie (reviver)- "Abigail likes you, %s. But she likes Lucy better." ( makes sense considering that Abigail's flower, Lucy the axe, and Bernie are on the list of: "sentient things that shouldn't be sentient." )
Wes (reviver)- "Abigail says she understands you, %s." ( to the people who have potatoes for brains, she says this because neither wes nor Abigail can speak.)I
Winona (murderer)- "Abigail and I will have fun with you!"
winona (reviver)- "hi %s. Abigail says 'thank-you'."
wortox (murderer)- "Abby and I will put your souls to rest!"
Wortox (fire starter)- "Abby and I know what you did, %s." ( that doesn't sound like they're judging you for your sins at all.)
Warly (fire starter)- "Abby and I know what you've been doing, %s." ( Yup, not creepy at all.)
Mod character (reviver)- "Abigail likes you, %s."
ice cream- "it has no warmth... Like my life without Abigail."
halved coconut- "two halves that were once whole. Where are you now, abigail?" ( probably in heaven watching you without your knowledge and consent.)
Ice cream- "ice cream could never replace Abigail." ( Abby's probably thinking: "OH but a spider can?" )
Banana pop- "I used to eat these with Abigail..." ( is it just me or is it weird to eat bananas on sticks. I've never heard of any body eating bananas like that...heck, Abby could've eaten a splinter...)I
Tea- "Abigail loved tea parties."
spicy chili- "Abigail hated spicy foods."
Abigail's flower (stage 1)- "it was my sister's flower. She's gone far away." ( I know these are pretty obvious too.)
Abigail's flower (stage 2)- "I can sense Abigail's presence growing stronger." ( well that's interesting. Being able to simply sense abby, even if she is dead.)
Abigail's flower (ready, held)- "Abigail is ready to play, but she needs some space."
Abigail's flower (ready)- "I need to show Abigail how to play." ( by 'play' she means ending the lives of animals for their own amusement.)
Orange soda- "maybe if I drank this stuff I'd return to my sister."
Lucy the axe- "hello..." lucy"... I'd like you to meet my sister. " (woodie's quote for failing to revive Abby is 'Lucy wouldn't let me hear the end of it if I didn't try.' Or something similar, suggesting Lucy cares about the twins.)
Codex umbra - "do you want me to read you a story, Abigail?" ( the other survivors: "oh heck no I don't like or trust that book" wendy: "I wanna read it." )I
Bent spork - "two utensils that are one. It reminds me of myself and Abigail."
mooncaller's staff- "as cold and lifeless as...well..." ( she doesn't say it directly buuuut when she said 'lifeless' we could all guess she meant abigail, because, unlucky for her, she isn't dead yet.)
Despawning (Celestial portal.)- "Abigail?" ( imagine despawning but then choosing her again and she saying: "dammit I was SO close to being dead..." )
Encumbered (carrying heavy object)- "don't worry...Abby...I got it..." ( this is just one of her quotes when holding a heavy thing, but only this one mentioned Abby in it.)
Failed to revive Abigail- "why isn't it working, Abigail?" ( Wickerbottom says it's because she's bounded to her flower some how. So maybe if the flower was completely destroyed...)
Rowing mistimed- "Abigail, perhaps you could take a turn rowing?"
formal set- "I'll only to to the party if Abigail comes too."
survivor set- "I carry on for Abigail's sake." ( well I guess this explains a few things, like why wendy didn't just commit suicide before she entered the constant and why she still tries to stay alive while in the constant.)I
Challenger set- "Abigail and I never fight." ( I guess this is one of the reasons of why their relationship is so strong... Now I want a don't starve persona game...)
UNIMPLEMENTED
Zeb (dead)- "say hello to my sweet sister."
inspecting self- "when I look in the mirror, it's like Abigail's here."
REMOVED
Sammy's wagon- "can I buy my Abigail back to life?"
small street light- "only Abigail lights my way."
Urn- "it's not Abigail's ashes." ( uhhh well based off of her other quotes we know that Abby was buried.)
Sapphire medallion - "money will not bring back my Abigail." ( what's with saying 'my abigail'? Sounds like a sans fan girl trying to 'claim' sans by saying 'my sansy')
Most characters (reviver)- "Abigail likes you, (name)" ( I just combined all of the characters into one to save time.)
Other wendy (reviver)- "Abigail likes you, other-Wendy."
Woodie (reviver)- "Abigail likes you, %s. And lucy."
Oof I've FINALLY finished typing all of these quotes...