This would be one Hell of a blow to the ego,
If you were describing this using Red Pill praxeology, you’d say she went through her “epiphany phase.” In other words, she’s getting close to the big 3-0, realizing she isn’t getting any younger and reevaluating whether the way she’s living her life is going to get her what she really wants in life.
In her case, she had a guy she had “mad sexual chemistry with,” but she recognized that he wasn’t a suitable guy to settle down with. On the other hand, the man in question was the type of guy she could see spending the rest of her life with, BUT she had no sexual attraction. So, I’m sure she did what so many women before did in that situation. She faked it. She oohed and ahhed and told him he was amazing in bed and either he was naive or she was just an amazing actor and he believed it.
Now he recognizes that he’s in what Red Pill guys call an “Alpha f****, beta bucks” situation. In other words, she had sex with that other guy because he turned her on and excited her. She’s having sex with him not because she wants him, but because she could see herself being with him long-term and so, she is using sex to help reel him in.