A woman who is up front about breaking up with her BF and using you for sex is as good as it gets. I don't know what else you guys are looking for. It could be a lot worse. She could use you as an emotional tampon, frame you for rape, pin her ex against you, or flake as soon as she feels validated (all typical female behavior). The woman the OP is describing is actually a breath of fresh air compared to a lot of women I have known in the past.
In all of my life history, I have never met a woman that was any better than what the OP just described. She was in a relationship. She broke up with him. She told you the truth. And she is up front about hooking up. What more do you want? A unicorn? They do not exist. The blue pill is simply self-hypnosis, just like love. Women didn't do it to you. You did it to yourself. You chose to believe in something that never existed.
It's kind of like women complaining about the knight in shiny armor taking her out to dinner and then trying to get his d!ck wet afterwards. She then goes off to complain to her female friends that all guys just want sex. Well, DUH. Did nature created anything else???? Or was it just your own self-delusion?
After 18 (probably even sooner), an attractive female develops a "pretty girl ego." She is incapable of melding into one with another person after that point. She has become too solidified. Egos cannot lose themselves into another person. It's like dieing and falling into a black hole. Egos can only manipulate to get what they want out of self interest. Attention, validation, riding the c0ck carousel, these all all just manifestations of that.
Women aren't the only ones with egos. Men have egos too. You ever seen two adults trying to make a relationship work? It looks like two pieces of concrete banging into each other. Their personalities are too rigid, and their egos are too concreted to lose themselves in "love". Romance is a game for kids (who hadn't fully developed their egos yet). Kids can meld into one. People who marry young tend to stay together forever because they have already become two sides of the same coin. For adults, it is a game of attrition, self interest, and manipulation.
When you swallow this pill, everything actually becomes more fun. You free yourself from your own expectations. You free people.