Defenders Hand blocking opponent's vision

[ballgame99]

Had this called against my daughter's club team. We were denying the ball to their best player in the last couple minutes, so we had a girl "faceguarding" her, and by that it just means deny her the ball all the time, don't worry about helping, etc. No hands in her vision or anything. Ref called T on us in a tight game without even warning her or us. Unless this is blatant, like the defender has a hand inches away from someone's face, I'm not sure how you can call it. And if that happens on an airborne shooter, I'm not sure I have anything.