The good news is once recovered there are no lingering after effects of parvo infection.
Good signs would be the dog stop passing bloody stool, cease vomiting and be able to hold down food taken by mouth.
You can read about Parvo here and it goes through all aspects of it really well
The recovery period is usually about 1-2 weeks.
Hope this helps you!
Oh she sounds really ill poor girl!
I'd say the work your vet is doing is helping her. But do read through the parvo site I gave you.
If you can't get the vomiting and diarrhea under control with 4 days of treatment, and she tested as positive for parvo, her odds of recovery would be lower.
But with that stopping and treament working those are positive steps towards recovery.
The only person who can give you that information is the vet who is treating her.