She softened the blow with the most comforting thing someone can tell someone else when it is over: "its not you, it's me." You know how I knew that was a line and not the truth? You should, you've been listening to me talk for a little over a minute, now. (alt joke: gesture at self and say nothing)
That's only slightly more comforting than saying "no you didn't do anything wrong, I'm just not attracted to you."
It doesn't matter what the situation is, both sexes use lines. Some girl could be dating a guy that still wears propeller hats, dropped out of middle school, drools on her during intimacy, and smells like a cat's lemony asshole, and she would still say it. (Easily modified to be family safe)
You probably think "why would she date such a goon in the first place?" Stay on topic.
It's not that one gender uses a certain line more, either; both genders are equally guilty. And when I was listening to her tell me that "it's not you, it's me," I felt like it was a word scramble, and I had to use an answer-key to figure it out.
"Ok so if she says: 'I need some time to sort out my feelings.' And the decoder says that all 'e's are 'a's, verbs are nouns, and that every first consonant is two letters back in the alphabet, what she really means is 'I want to bone the trainer at the gym more than I want to bone you.'"
People don't like to deal with pretense like that! It's like dating The Riddler from Batman! Holy shit it must be impossible to know why he would break up with you. By the time you figure it out he's already moved on and robbed a bank. I couldn't think of a sexual analogy for this statement, but believe me: I tried.
Edit: I'm still unhappy with this bit. I just don't think I'm approaching it from the right angle. Either that or I sound too bitter for it to be tongue and cheek. I can't figure which, but my plan is to just rewrite it over and over with different approaches until I figure it out.