I didn't see your previous post, but the fact that you've raised it again indicated the answers weren't helpful.
I'm sure there will be financial help but it will probably involve Social Services. This is something everyone tries to avoid, but they are kind caring people, very overworked, but I'm sure will help you.
We have several members with legal training who I'm sure can offer sensible advice on any financial help you can get from the govt.
Basically, are you able to look after this girl through the coming difficult years - physically, financially and emotionally, (remember how your own daughter was). Have you been super-nice to GD and let her have her own way? Is that going to have to change so that she helps you and does her share of housework and isn't just treating you as a hotel.
Its a h^all of a commitment.
Have yoi had a good in depth discussion with GD - does she understand your problems?