My best friend always takes my aux cord?

It's MY aux cord that I bought with MY money in MY car. Not that I care if she plays music but the problem is how she does it. If we get in the car and I grab the cord, she takes it out of my hands or unplugs it. Then we have a tug of war for the cord for like a minute. When I win she gets mad and says like,"I hate you. I seriously hate you right now." in her car, I don't play music unless she asks me too because it's her car and it's just courteous to let her play it. One time she unplugged my phone mid song, unplugged the cord, and threw them both in the back seat. I would have no problem with it if she asked, and I'd most likely let her. But this **** is getting old how do I make her stop