OP, All I have to offer is

.
My sister got lice in kindergarten and of course, we shared the same room-I had them too. Not fun going through the RID treatments as a kid. The only thing going in our favor was that my mom insisted on short haircuts and we had dark brown hair with red highlights-the nits were easy to find. The school nurse also suggested washing with Lye soap. It was a wonder no one else in the house got them.
Last February, my boys got them. We weren't sure if it was school or day care. Let me tell you, I feel for you, because I did 14 loads of laundry in 24 hours, picked two heads, had mine picked and thanked my lucky stars that we have leather furniture and allergy bags on our mattresses.
So, I did all the treatment and a week later, my daycare provider went BALLISTIC on me, as she thought my boys brought it to her place and one of the toddlers now had it. I went through round two with my boys, even though all the soft things were STILL in bags in the garage in my one month banning (I'd been to the website). Another 14 loads of laundry and a sleepless night. Sprayed the cars (again), changed the linens out (again) and decided to shave my son's heads. Older son loves his hair this way, but we had to rid my younger son of his beloved curls.
Older son has coarse, straight hair, he'd only had three or four eggs and two nits. Younger son has baby fine curly hair-his head was like your daughters. My hair is even finer than his. The reason why the got me is that he'd been feeling feverish and climbed into bed with me a few days before we found out they had them.
After the paranoia and angst that we caused all this, I even cut my hair short. Both son's teachers were so very kind in all of it-they told us we would not believe how often it happens. I know the shame you feel-I felt it, too.
Then a month later, my daycare provider came to me shamefaced. It ends up that the toddler was the one who was the source of it. Her mom had read my daycare lady the riot act that it was from us and the school and she came to find it was from her neighbor.
The lesson I learned is that lice are insidious, like fine hair that's clean and live through the promethrin shampooing. I'll never judge anyone for having kids with it, because mine had it and it wasn't from being unclean. The little girl who brought it in wasn't, either.
I didn't talk about our ordeal on the DIS because, like you, I was ashamed and afraid of what people would think. Since then, I can't tell you how many times I've heard of people who were dealing with it.
Hang in there, I hope that DD's shorter style will help eradicate it from your life.
Suzanne