My grandma's dog had the top part of her toe ripped off, it never fully healed because she kept licking it. Even years later she would suddenly start licking it obsessively and reopen it. I think since it's a toenail and that will grow back it will probably be okay. If it's just barely hanging on I'd go ahead and remove the old toenail. I doubt she's leave it alone though and you'll probably need to get her a cone. I'd take her to the vet monday just to get it checked out but I think you can buy cones at petsmart.
If you can . Go ahead & cut the toenail off or trim it so she doesnt keep catching it on things . Or itll eventually fall off on its own , but keep it clean with peroxide . When I owned my kennel we lived by this .