How yall doing. Some background: I'm a senior in high school now, and I've come a long way socially. Freshman year I was a beta orbiter and bitched about being in the friend zone. I go to the gym and have been losing weight, I'm more confident. Looking for a prom date.

The question: One of my close friends (male) has been family friends with this girl for the better part of his life. She has a boyfriend who went away to college, and cheats on her regularly. She is aware of this but they were together for four years so she's a bit attached to him, less so more recently. I've taken a liking to her and my friend has been mentioning to her that she should go to prom with me and date her, and she responded with "I have a boyfriend". Let me say she's strongheaded, and in the past when someone tried to get her to date them she'd shut them down quite angrily. So her saying "Noo I have a boyfriend" while giggling is evidence she's open to the idea. I wanna pursue it. How do I get her to go to prom with me, and make sure she understands it isn't "as friends"? I know prom is in June but I wanna turn this into something before then.

For reference she's dirty blonde, face is an 8 and body is a 6.5. About 5'5". I'm 6 ft and relatively muscular. Turning 18 on November 17th and getting a car in less than a month so I'm hoping to hit the gym much more frequently. Thanks in advance for the advice.