I (30F) can't stand my boyfriend's (31M) close female friend (22F).

I apologize in advance for such large walls of texts T-T
My boyfriend met this woman through mutual friends three months before he met me off a dating app in December. I've been told in those three months, they became close and he'd confide his problems to her. She started dating his best friend casually. In March, his best friend dumped her and she was devastated. She became really needy and started hanging out with us at least once a week. I wasn't seeing him often then, usually only on weekends, so I felt like I wasn't getting enough alone time with him. I also didn't understand why she was always around. If my male friend just got into a relationship, I'd back off and let him spend time with his new girlfriend. He also made things worse by inviting her to what I thought were dates and I'd find out when we got to the location. For example, he and I would have plans to go watch a movie. She'd ask him if he had plans and he'd invite her to come along without telling me. We would get to the theater and low and behold, she'd be there. This happened a few times and it drove me insane.
I started noticing they'd touch each other more often than I'd like. He'd guide her walking by touching her lower back. She'd reach over and squeeze his biceps. When she wanted his attention, she'd touch his arm. The last straw was when we went to a rave in May and we met up with her friends. My boyfriend and I wanted to see another DJ and get some alone time, so we told her we'd be right back. She didn't want us to leave her with her friends but we told her we'd be gone only 30 minutes. When we came back, she was having an anxiety attack and crying that we left her. Her hands were numb and trembling, so she asked him to massage her hands, which I thought was incredibly inappropriate. Not to mention earlier that night, I was leaning back on him cuddling while listening to one of our favorite songs. He then put his arm around her so we were in this weird three-way cuddle. His reasoning was that he didn't want her to feel left out...
I confronted him shortly afterward and told him that their relationship made me very uncomfortable. I didn't want to make him choose and knowing myself, I felt like this wouldn't work because we clearly have different boundaries. He told me that if he had to choose, he'd choose me. He suggested that I tag along whenever they hang out so I could see that he's not doing anything inappropriate with her. I told him I didn't want to do that because I don't like her as a person. She's not very bright, we don't have much in common, and whenever we did hang out, she'd talk endlessly about her life and not include me, making me feel like I'm third-wheel. My boyfriend doesn't talk much and is a good listener, so I can see why she enjoys being friends with him. But I don't understand how he benefits from the friendship. I also don't understand why a 31 year-old-man wants to be friends with a 22-year-old woman, who are both at completely different phases in life. As an outsider, doesn't this just appear creepy? One red flag I do see is that all her "close" friends (including my boyfriend) are from the last 2-3 years, most of whom she met at work or the gym, and they're all over the age of 28, the oldest being 36. She doesn't have one friend from grade school, high school, or college that she hangs out with, which I find odd and telling (we're all locals in a large metropolitan city and grew up within 20-minutes of each other).
It was at this point he suggested that he maintain a "text/online" friendship and not hang out with her in person anymore. I told him I didn't want this but he convinced me to give it a shot. There were a couple of times where we had to go to social events and see her, which I had no problem with. However, two weeks ago I went out of town and he told me he was going to get brunch with her and her new boyfriend. I was livid. To me, he broke his word and it made me feel stupid for trusting him. He told me that he never wanted to stop hanging out with her and only told me he would, to placate me, thinking that I would eventually get over it. He thought that I was uncomfortable with her because I thought she possibly liked him more than a friend (this was a passing thought but not my main concern) -- so since she was in a new relationship, it was okay to see her again.
We got into a huge fight and due to conflicting work schedules, we didn't really talk or see each other for 1.5 weeks. When we finally talked, it was a 6-hour discussion about why I think her actions are disrespectful and how he doesn't think they are. He doesn't think it's a problem that she asked him to massage her hands because "friends help each other out". He believes that it comes down to trust and if I trusted him, this wouldn't be an issue. Meanwhile, I think this has nothing to do with trust. I see her touchiness and behavior as outright disrespect to me. And the fact that he doesn't try to negate her behavior by not reciprocating, is also disrespectful. He's concerned that if it wasn't her, it'd be someone else and what if some other female comes into his life and the same thing happens? But I don't have any problems with any of his other female friends; just her. I don't know I'm being naive or if it's because of the age difference, but I think most people our age wouldn't behave inappropriately with friends who are in relationships, so it wouldn't be an issue? To be clear, I don't think she has ill intentions; I truly think she's young and naive. But it's not my job to tell her what's appropriate and not.
However, I didn't want to give up without trying so I suggested I have a talk with her. A few hours have passed and I'm having second thoughts. Back in May, he actually suggested this, but I didn't want to because I didn't think it would make a difference. Maybe she'll surprise me, but I know so many people who either become defensive or agree/apologize, but keep doing what they're doing. I also don't want to be cast as the "villain" or "crazy girlfriend". Am I overreacting? Clearly he and I don't see eye to eye on what's appropriate and not -- so is this a dealbreaker? I feel very conflicted and don't know if this is worth saving since he and I have only been dating for 10 months.
tl;dr
I don't like my boyfriend's close female friend. I believe she behaves inappropriately around him by maintaining a "physical" relationship. Should I confront her? Is this a deal-breaker?


Source.