Earth bath has a tea tree oil shampoo as well as an oatmeal and aloe vera shampoo. I swear by all of their shampoos. Your friend may also consider to use some actual tea tree diluted in water. Good luck to her and her dog!
I use Earth bath shampoos and dilute them and then use lots of earthbath conditioner. The less they bath the dog, the better though probably because any shampoo will strip oils from the skin.I hope the treatment is a success!