How do you cure her in the first place? The only things that come up for me are the basic ally commands and to give me bloodcursed arrows. Oh, and if she cures herself, will I be able to get anymore Bloodcursed arrows?
If you ask her about curing herself before the main quest is over, then she won't do it. But the option to comment on it should still be there, she just says something along the lines of "You've asked me this before, I'm not doing it". The only way to get her cured is to never discuss it before the main quest ends.
Can she still infect you if she is cured.
You do know what cured means... right?