Jealousy over long-distance boyfriend?

My boyfriend and I have just finished our freshman year of college, and have been dating for 4 1/2 years now (since just about the beginning of high school). Last fall we went off to separate colleges about eight hours apart. It was really really difficult at first to the point where I'd cry myself to sleep every night, but by now it's manageable if I keep myself on other things throughout the day.

There's one problem though that I can't get out of my head, and I honestly don't even know why it's making me so anxious and insecure. My boyfriend has always had his fair share of female friends and I really didn't mind at all back when we went to high school together, obviously because I knew them and I felt very secure in his love for me. Now that we're long distance though, every female friend he brings up in our conversation makes me a little more anxious, a little more insecure, and at first I was able to control these feelings by telling myself that I was overreacting--my boyfriend has always been extremely caring and loving and he has never for a second given me any reason to believe he would cheat on me.

There's this one girl though... Let's say her name is Jenny. I first noticed her when I noticed her posts on his Facebook wall, and he started bringing her up in conversation saying things like, "Oh, Jenny and I sang that song at karaoke!" or telling me they'd gone to lunch, which made me a bit jealous obviously, but I knew it was groundless and dismissed it. But then they started getting more and more familiar with each other, to the point where she'd post a picture she took of him on her Facebook and call him the "ugliest guy on the planet, and who would wanna date you?" which annoyed me for obvious reasons, and stuff like this on a daily basis, where they would have fake 'arguments' about which one being more ugly or stupid or fat, which sounds strange but I think is her way of flirting with him. Other people would post stuff on his wall too like, "You and Jenny are always at it," and "Wow, you guys are like a married couple," and he stopped mentioning her to me.

One day a couple weeks ago though we were Skyping and she came into his dorm room and randomly sat on his bed and he asked her what she was doing and she just said, "My room's stuffy and I needed some air." She then just curled up on his bed like she was gonna take a nap and went under his blankets, and my boyfriend just returned to our Skype conversation without saying anything. Even though I felt like not saying anything either, I was really uncomfortable and so I asked him if he was okay with her sleeping in his bed and he said, "Oh yeah, she does this all the time," which I didn't know anything about. Even though I was still uncomfortable I tried to let it go at this point. But after a while she got up, said she was cold, and raided my boyfriend's closet without asking him, grabbed one of his jackets, and put it on. At this point I didn't know whether she was actively trying to make me jealous or if she was just really insensitive. She said something along the lines of, "Your jackets are really comfy," which meant she'd done this before. I had to go to the bathroom (and also sort out my head) so I left for a little bit, and then when I came back my boyfriend was talking to Jenny, and because I wasn't in view of my webcam yet I stood there for a bit listening to their conversation. Jenny was asking my boyfriend whether I was the jealous type, and he said, "Nah, not really, we trust each other," and then she 'jokingly' strokes his hair and says, "Would this make her jealous?" At this point I'd had enough and I go in front of the webcam and she takes her hand away, and tells me that my boyfriend has a super-comfy bed but I shouldn't be jealous of her because she would never date his ugly mug, they're just friends. Which was offensive on like three different levels.

Another thing was when I was visiting him one weekend and we were pretty hot-and-heavy making out in his room, she just barges in (we had just enough time to crawl under the blankets and pretend we were sleeping) with the room key she borrowed from my boyfriend's roommate. My boyfriend told her to get out at first but she sat on the end of the bed and so he just stood up and talked to her for like twenty minutes while I was hiding under the covers because I wasn't wearing a shirt (he had all his clothes on still). Apparently she wanted him to come out with her and her friends and climb up this hill with us to see the view, and when she saw me she was like, "Oh, I forgot she was coming this weekend! She should come too!" like I wasn't just lying awkwardly right there. She never once directly talked to me. My boyfriend finally got her out of the room but five minutes later she knocked on the door again really loudly asking us to come out with them, and then fifteen minutes later again. The one time that she actually talked to me that weekend was to say, "He's so annoying and ugly, why are you dating him?"

My boyfriend said "she can be annoying sometimes, and insensitive, but we get along well so I don't wanna just cut that out of my life." I don't know though... It's not that I don't think my boyfriend is gonna cheat on me exactly, it's just that I don't like that he allows this kind of behavior and that he's around this girl who thinks it's totally okay to say and do stuff like this--and that other people will see that he's okay with it (a lot of people at his school who don't know better just assume that she's his girlfriend). I don't let guys onto my bed because I feel like it's an intimate, personal space, and the fact that she just sleeps on his bed whenever she wants (once, apparently, she barged into his room at 1am and fell asleep there for four hours so my boyfriend had to sleep on the floor) just makes me really really upset.

Whenever I bring this up though, I feel like a super-controlling, insecure girlfriend, and that's something I've never wanted to be... It's obvious that they're good friends and besides all the annoying bits, they're actually pretty similar and it's easy to see why they get along so well. But still, we're long-distance and I feel like the anxiety is tempting me to play mind games with him, like trying to make him jealous, or something.

Any advice on how to talk to him about this? And does anyone have any opinions on where her actions could be coming from, and what she could possibly want from him? And why does he let these things happen? I know he loves me, but still, it makes me sad and anxious.