It's pretty typical for a female to sit on a male when she's had enough of him -- she uses her bulk to control him and block irritating courtship behavior. Sometimes they do it when they're not receptive at all, not receptive to a certain male, after they've locked and the female does not want to lock with him again . . . really, whenever they decide breeding is over for a given session. (The reverse of when a pair is locked, and most males use the lower half of their bodies to control hers.) Some girls do it this way, some are more subtle. When I see something like this, I give the pair a couple weeks/a month before reintroducing. After that, I kinda play it by ear as to whether or not to try another male or wait for next season.