[adamanteus]

I don't think you could worsen the situation by feeding her. That said, you might worsen the situation by just bothering her, stress is a big thing for snakes. Chances are she's quite able to fend for herself, despite the scarring. Mice are probably not the best thing to offer to a wild Garter, better with earthworms, fish or frogs. Unless you intend to catch her and keep her as a pet, I would suggest you content yourself with just watching her progress. I'd like to see a photo of her, if you can do that, I'm sure many of us would.