Just give everyone an idea, my boyfriend and I have been dating for almost 2 years, and he's know her for about 4-5 months, which he met her at school.

First time he ever went out with her, he was at a bar, and I was hanging out with my friends that night.
My boyfriend got intoxicated to the point where his friend had to take him home, they arrived at 4AM, and she didn't leave till 6:30AM.

After that event, she started going to my boyfriends friends house to hangout with him, which than she started making friends with my boyfriends friends.

Lastly, they constantly talk through text.
One evening, my boyfriend and I decided to do our own things, we agreed to come back to his house at 12AM, he arrived home at 5AM in the morning, AND saying goodnight to the girl through text.

I don't personally know her, briefly met her as she was walking out of my boyfriends house while they were hanging out with people.

I've told her how I felt through Facebook, and told my boyfriend personally, and they still continue to talk, even when I'm around.
My boyfriend doesn't even have the decency to say goodbye to her while I'm there, we barely get to spend time with each other since we live an hour and a half away from each other.