Every one has their own way of retwisting. Me personally I like to palm rolling, but then it depends on what is going on w/ their hair. I might use my comb. Then it depends on the length of the hair. Locs thin out depending on the size of them, the longer it grow the heavier it gets.
I have noticed that when some people keep their hand in their locs, they tend to weaken, then they fall out. So be careful.
If you are pleased with what she is doing let her know. If she can not do what you ask find someone else. Question: do your hair look neat?
I have been doing locs since 2002, and not seen anyone hair weaken from ME palm rolling. It only thins if you put to much tension on the hair.