Unfortunately it is hard to say, in our son's case he has lost some, some due to surgery and some due to them rubbing against his eye. They take a long time to grow back so it is kind of a wait and see thing. My son did have some that grew back and others did not, the same with his eyebrow.
I know that is probably not the answer you are hoping for but you can take comfort in the fact that she will be able to wear mascara at some point and use false eyelashes if she wishes, so that is a plus!
Good luck to you and I hope it all turns out as you hope!