Off Topic: My Crush Just Mentioned Their Boyfriend/Girlfriend ...
No, this didn't just happen to me. I'm actually not crushing on anyone at the moment, unless you count Alan Rickman's turn in Sense and Sensibility as Colonel Brandon, and even that is just one of those meaningless but pleasant fantasies. No, I'm writing this, because for about the billionth time I've just seen someone put this question online and it's one of those questions that really bothers me.
And here is how I would like to answer the question:
If someone mentions their boyfriend or girlfriend while their in conversation with you, then the healthiest thing to assume is that they are talking about that person because they love them and because that person is a big part of their life. Maybe they're at a point in their life where they have just met this person who they think is completely amazing and they cannot believe how lucky they are that he or she wants to date them. They're so ecstatic that they just can't help talking about that person. Maybe that person is on their mind a lot.
Finally, it's probably not a reflection on you. Unless you make it obvious, your crush isn't going to know that you have a crush. Stop analysing, and stop asking yourself if you did something wrong. Because you probably didn't do anything. Just accept it for what it is and move on.