I mean, I can agree with the overall message of the post to some level. Just not like that.
I have dated and known girl like the one in the OP though and it is true. They don't realize what they had until it is gone and then they want it back, but they cannot have it and it always kinda sticks with them somehow.
I was with this girl for almost 3 years, split up 8 months ago I guess(she knows better than I do), she cheated on me a little over a year in and I foolishly stayed with her. Love and all, but it was a shit relationship afterwards, long story. Anyways to wrap it up I realized one day I was really unhappy with my life and she was bringing me down a lot and I just got really tired of her shit, so I told her I was out. She cried, she threw a fit, she came back a week later and told me how much she loved me etc. etc. I told her I care about her and wish her well, we can be friends down the road, I hold no grudges, but this is what I want and that is that.
I banged her last weekend in my new place. I told her this is strictly sex, nothing more, she agreed, she is fine with that, but if she is trying to get back in and get back with me, it isn't going to happen.
Another girl I know dated one of my best friends when we were kids. They were together from 15 to 19 years old and she was kinda shitty to him. Left him a bunch of times for other dudes etc. Finally he had enough and he has moved on. He is getting his BA in EE in May, had a killer interview yesterday and is happy with a new girl who treats him right. The old girl has 3 kids, all different dads, a shit job, barely makes her bills, and lives a rather dull life now. 10 years later she still regrets treating him like she did because she knows he would have stayed with her(he would have if she was good to him, he really did love her), especially now seeing how much he has gained and where he is going in life.
My ex-wife is all of a sudden more interested in me again after she left me to become a lesbian for a year(she has a boyfriend now). She isn't really happy with her current man and she sees how I have grown and how I support myself and our daughter on my own completely, on top of my gym habits, school, etc. She too treated me a bit like shit and when she left I was devastated, but now I am happier than ever and I just chuckle when she cracks a half joke about how she had a dream we got back together.
Not saying only women do this, but I do not date men so I cannot attest to them doing the same thing with the women they date.
People really don't care or realize what they have until it is gone from them and the door is locked and they cannot get back in.