Hi, Cinthia --
I think it would be a good idea for you to speak to the parents of any of the children you think might have lice. You could definitely do it innocently -- such as "my daughter's gotten lice several times this year from contact at school. Since she and your child are friends, I wanted you to know so that you could check your children, in case they'd been exposed. We've been using product X, Y, and Z and they've been helpful..." etc.
I guess another alternative could be to tell the teacher -- or principal -- that you are not going to bring your daughter back to school until the problem has been addressed there. It's a public health issue, and there is no reason your child should have to be subject to repeated infestations without the administrators addressing the situation with the parents of the entire class. Since you have such a short time before you're moving, the point may be moot. But, at her age, I think I'd keep my daughter out rather than have her keep contracting lice.
Best luck!!
H.