She misunderstood the story, but let's just say I did a bad job explaining it too.
My post was not about a girl who lied to me about having a boyfriend. It was about a girl who purposefully withheld the fact she had a boyfriend so I wouldn't find out she would be soon be cheating on him, with me. When her roommate asked about the boyfriend, the girl made up the excuse that they were "on a break" as a way to rationalize the cheating. Contrary to popular belief, the purpose of the story was not to brag about having someone else's girl, it was to show how there is a very thin line between being in a relationship, and being single.
Some girls will lie and say they have a BF as a "polite" way of saying they aren't interested. It's not really a huge diss like Mewothkips makes it out to be, and it isn't some new technique reserved specifically for the creepiest of creepers. It's easy, and effective, andIf a girl says she has a BF you could assume she does, and stop talking to her but you also could keep talking to her as a friend. Maybe she lied because it's an easy way to filter out guys who only see her as a sex object. The typical guy will run off after she drops the boyfriend line, so if you actually try to get to know her as a person, despite thinking she isn't available, you will show you aren't just looking for sex. That's going to leave a good impression whether she was lying or not. If she really does have a BF that's cool too - you could end up with a new friend, and new friends are always nice. Plus, hot girls have hot single friends.
People will find ways to ask about relationships indirectly. For example, a girl asked me "do you live with your girlfriend" and I said I didn't have a GF. After that she was a lot more flirtatious. Questions like that are part of normal conversation, so it's not a big deal or huge risk.