This is kinda sad.
Sad that it took this long for her to figure it out when this is what social conservative women know already!.
The connection between relationship and sex is one of the many reasons why there should be no sex before marriage.
It's like that old adage: why buy the cow when you can get the milk for free?
When you have sex before marriage, you're selling yourself cheap. You might get sex now, but you're selling yourself at a reduced rate.
You end up with what you'll accept. If you accept no-lifetime commitment, if you accept sex before the relationship that is exactly what you're going to get.
When men invest in "earning" you, they're probably more likely to invest a lot in keeping you.