hands in face

[chas]

I was doing a Jr. High girls game last week and during a throw-in(s) a certain girl(she was the only one)would wave and clap her hands as close to the eyes and face of the girl doing the throw in. I will be doing this team again in the future and was wondering if there is a point where her actions are illegal? Would just keeping her hands steady but as close to the face as possible merit a warning? What do you think?