Hey B.,
Oh do I feel for you. We went through something similar with our daughter. I think you are right to keep her from your children until she is rid of the lice. It is our experience that if she is stll having problems with it then it was never really gotten rid of to begin with.
I would treat everything in your house again and make sure your children and you and your husband dont have it. Then you have to check her throughly before you let her back in the house. I know you love hr and this isnt meant to sound mean, just cautious.
I know you said you used mayo, but did your wrap her head with a plastic bag for 30 minutes with the mayo on? If so, make sure you pick through every single strand of hair for the nits. The bugs are a sign that she has had nits for a while which means you didnt get rid of them when they were nits.
If you do allow her to come back, keep all her clothes and bedding and toys that she brings outside until you know she is clear.