When the ball is on the ground a player is allowed to block/obstruct an opposing player from getting to the ball with the body, it's called boxing out and completely legal, the ref was wrong and a bad call.
Here's the rule, in its entirety:
q. Detaining: Detaining an opponent at any time by holding or pushing against her body, clothing or crosse with an arm, leg, body or crosse. A player may not hold her crosse in such a manner as to restrain or hold back a player.
You have the wrong sport for "boxing out". That's basketball.
I didn't see the play in question, but there is a difference between "pushing against her body" and just getting in the way. I'm sure you've seen a ball rolling out of bounds and a girl from the team who will get possession blocking a girl from the team it is going out on from getting it. Was there a foul called then? "Boxing out" is allowed if you don't initiate the contact and "push back."
