Ever since Next of Kin I've been looking forward to what the next refresh-related short would entail. It is exciting to see anything about Willow's story because she has very little back story compared to other characters. For instance, she is one character who doesn't have a lot of interesting quotes about her past. I can't wait until the short comes out, so I'm going to over analyze the heck out of this teaser and see how it adds up when it finally releases.
To start, Willow looks very young in this. It's not clear whether this shot is from a short flashback or if the whole short will be about her childhood. Either way, it seems like this could very well be a depiction of a significant formative event in Willow's life. And obviously, it will probably have something to do with fire. Maybe it will even be the origin of how she became obsessed with fire in the first place!
The location looks to me like an old rundown orphanage. We already have hints at Willow being an orphan with the artwork of her unimplemented Orphan Skin. While tragic, a parentless background makes sense for Willow's character as well as growing up in an environment like an orphanage. One thing I remember learning about children in orphanages that I connect to Willow a lot is their inclination to collect/hoard things. This is because being in an orphanage where kids have little agency/independence, the few things they do have become very important to their sense of personhood. Having personal property is a way to feel human. I feel like Willow's dedication to Bernie is a reflection of this, in a way. (I don't remember where I learned this, so I don't have a source, but I thought I'd mention it.)
A big detail from the teaser is that the color pallet is mainly blue. Additionally, the windows look like it could be winter outside. This can provide an excellent contrast with Willow's favored element, and is perhaps the reason as to why she took to it. In fact, one of her new perks as listed in the announcement post is that she takes more damage and loses sanity while freezing. Her sensitivity to the cold may go back to what happens to this short.
As for what exactly is going on in this scene, it looks like the typical strict orphanage lady pulling a reluctant Willow down the hallway, perhaps back to bed (the lantern implies this is a night scene). Considering a lot of her rework concerns Bernie, and we haven't gotten a full explanation of his role in her life (besides a few quotes she has for him), I'm going to say its Bernie she's reaching for. I'm wondering if we do see Bernie, if he will look more pristine than he does now.
–When examining Bernie
–When examining an active Bernie
–Unimplemented Forge Bernie quote
That's all I have on this one image right now. The only other thing I'll say could happen: this orphanage is likely not going to survive this short.
Because I love challenging my own theories, here is some counter-evidence suggesting other possibilities for this short.
The building could be Willow's house, and to go with that, the old lady may be her grandmother (or grandmother figure). This is based on her DST quote for the Lesser Glow Berry: "It feels like grandma's hands." (which is significant because I find that DST quotes are more lore-heavy than base game/DLC quotes). I am also struck by her quote for the Walrus Camp in the base game: "Why does everyone have a nicer house than me?" This could be indicating that she once had a house, and a terrible one at that if the walrus igloo is nicer in comparison. The building in the teaser looks fairly terrible.
Dev Stream Update
The surprise DST dev stream on May 5, 2019 gave us a preview of the main menu for the Willow Update. So far these character updates have gotten a tie-in animation loop for the main menu background, and they coincide with the animated short.
This one features an inflamed, angry looking Willow clutching Bernie. She's standing in what looks like the same building as in the first teaser, but it is now in a bright red pallet as opposed to the blue. This might be the house on fire, considering the black lines which look to be ashy burn marks. My prediction that the building is not making it out of this short seems to be on the mark so far.