I would just buy a pack of those small elastics at dollarama (400 in a pack, kind of like the ones used for braces). I have had this with a few kids. I tell the parents that the hhair is bothering the child and then tell them about these elastics and how great they are, where to get them etc. Then when she comes in the morning if they haven't done it, throw one in her hair. I have done this with a few kids now and the parents always start doing it at home.