i bought a retired racehorse back in october..when i first got her she was pretty thin and really calm..she would let anyone do anything to her and she didn't act up at all..but now she's putting the weight back on and becoming very spoiled..now anytime i'm handling her she acts up in some way or another..she tries to bite when she doesn't get what she wants and she can be quite pushy..what is a good way to get her to be not so pushy and to stop biting?