Refer her to a web site I referred my parents to in my child care facility.
headlice.org
It gives good advice about treating head lice the right way, without chemicals and pesticides. Tea tree oil can be bought at lots of drug stores or places like that and you just a drop or two to the entire bottle of shampoo. It really stinks so you really don't want to add more.
Head lice like clean hair. They can stick their babies (the nits) to the hair if it's clean and not oily. Head lice can only get from one person to another by direct contact. Tell your friend to teach her child to not put on things worn by other children, like hats, wigs, etc...like dress up clothes at school.
Our local Health Department states that head lice is at epidemic levels. It is everywhere and no one is immune to getting them. It is NOT a big deal.
There are LOTS of old wives tales out there about how to clean and get rid of them but the fact is just vacuuming the area get the bugs up. The web site covers all that. She can get all the info she needs there.