Is it normal to have to beat this girl up for this

I am a nonviolent person unless pushed over and over. Cheerleader, popular, likes to be at peace with pretty much every group. For an attractive young female, I have a pretty powerful physical wrath.  Long story short, senior year I was friends with a girl who had an amazing boyfriend, though she would always try to sneak behind his back to fuck mine. Caught her through text messages saying she wanted to fuck him. Broke up with boyfriend. confronted her. She apologized over and over I leave in tears. Only to find out an hour later she texts my boyfriend saying untrue things about ' how I fucked three guys behind his back and do all the time." I wasn't even going to tell hers but she assumed. A week later I forgave her after 8 text pages of another Again I confronted her in person after and told her if she were to ever cross me again I was going to beat her ass and to not underestimate whether or not I would. She agreed and said "seriously  i wi t ever talk to him again even if yall arent dating because i have my boyfriend .please if I ever did it again, which I won't! Please beat my ass because I deserve it" boyfriend and I work things out a month and a half later. We're back together and me and this girl at a party together, she brings up the subject of how she would never do that to me again and how sorry she is and how much she appreciates my forgiveness. I find out from my boyfriend that they fucked. TWO. DAYS. LATER. Kicked his ass to the curb for good. This girl found out that I knew and was literally shaking in her boots scared. I come home to a bunch of apology messages on Facebook that I leave unreplied they're bull shit. She knew what was coming.. I didn't want to do this at all, but I am a person of my word. Next time I saw her, I'm not going to lie but beat the living hell out of her. I actually didn't think I had it in me. This girl told me to beat her ass, I kept true to my word after 3 times of forgiving. Yeah I know "violence isnt the answer" but this girl crossed me three separate times consciously. So is it normal? Is it normal to have to deliver an ass whooping to someone after cheating on your boyfriend with mine, crossing a forgiving friend more than twice, developing the tactics of a pathological liar. And  for someone who absoloutley INSISTS on learning the hard way. And even telling me to do so. Some people need an asskicking to set them straight. An honestly, if I were to do this to someone, id expect the same thing, if not earlier, and with no excuses or complaints. I deserved it.