Why are girls so difficult?

My friend (I'm not going to say her name so I'll use Angela) pushed me when I told her to stop pushing me when I was giving her something back, but she pushed me hard and my milk spilled on the floor. She just walked away without apologizing, so I decided to play a small prank on her (the prank was nothing big, but she did it too many times to me without apologizing) and she told me to go to hell. I was pissed because I apologized and she didn't. I said sorry to her so many times, but she just insulted me. Should I say sorry again or leave her alone? I was thinking why and screw her, but I don't know. That's why I hang out with gamer nerds and not girly girls. What should I do?