Sounds like she is being young and playful. A good bullwhip or a hot shot will teach her that she has her space and I have mine and those spaces do not need to cross. I see all these post about shipping heifers and young cows just because they are high headed, standoffish, good mommas protecting their babies, or haven't learned to stay back and I just shake my head. I have known a few people who got killed by cattle every single one of them outside of rodeo was killed by a cow they considered gentle or a pet. When I help people work cattle I would rather work a bunch of high headed cattle than a bunch of pets.