How to handle this anger?

So I have this emotional problem with my boyfriend and his family….

You see, my boyfriend had this close friend that was a girl ever since middle school. They were pretty close for quite a while, even when I came into the picture. She had a boyfriend of three years while I was dating my boyfriend, so at the time I didn't really think much of their friendship until her and her boyfriend started having problems. That was when everything started changing. She started coming over a lot more, spending time with his whole family more, and invited him and his family to just about everything. Even buying and making them presents. Nothing for me though. The only thing I got was "Oh, yeah sure! She's such a nice girl! She's a good friend!" …….Sure? The supposed "friendship" me and her tried to maintain never really felt right. Maybe it was where we were too different? Or how she would constantly come over to spend time with my boyfriend and his family? Yeah. I about snapped a few times. His family never helped the situation either by trying to invite her to every camping trip or road trip they had. Did I mention there was even a time she tried to get "dirt" on me? She was such a great "friend" to me.

To make things even worse, me and my boyfriend did break up for about a week because of our arguments revolving around that subject. This resulted in her confessing that she really liked my boyfriend and them kissing and flirting for the whole week. Of course, that didn't last long. My boyfriend came back to me, confessing everything that had happened and telling me he made a mistake and that the only reason he even kissed her in the first place was to forget what had happened and try to move on, but he couldn't and that it felt wrong. I was shocked he admitted it so quickly, but I couldn't be mad at him. I had almost done the same thing with someone else he had hated and forgave him and we became a close couple again. Later that day you could probably guess she was pretty mad and upset about what had happened and was quick to say how much of a crybaby I was and how I didn't deserve her best friend in the first place.

So, fast forward to NOW. Things are a lot different. She no longer comes around when i'm near and I never see much of her anymore. My relationship with my boyfriend has gotten a LOT better, minus a few arguments now and then, but better. I guess you could say that life is pretty peaceful, but there are still a few problems with my boyfriend's family. In the beginning and around the middle, I thought they would have been willing to let go. Instead? They still invite her around when i'm not over and still try and hang out with her even when my boyfriend isn't around. His mom has even taken her to the lake with her once over the weekend. I felt pretty hurt about it when I found out. No matter what I say, his family, or his mom rather, still tries to be close with her. Why? Because of how she acts so much like her and i'm so different in comparison.

I may be a crybaby about it I guess, but I feel pretty hurt when I log onto Facebook and see his mother post comments about how "special" the other girl is to her and that she is practically her other mom. She doesn't get it either how that hurts my feelings. My boyfriend has tried explaining to his mom about how I feel, (He distanced their friendship a lot for the sake of our relationship.) Of course his mom still chooses to blame what had happened during the break up his fault for making me and that other girl so angry at each other. He's the reason why she can't invite the other girl over whenever she wants and just have a big "girl" time together. He gave up after a while since he didn't want to argue with his family about it anymore. I didn't blame him and didn't want their to be any issues so I just dropped it.

In any case, I still have a lot of bad jealousy issues when it comes to this girl. It's built up in such a rage now that I can't even look at her without my face heating up. I don't know what to do about his parents either. I feel like everything is my fault. (Which it really is….but I didn't know what to do with her hanging around so much. I felt replaced…) I feel so guilty for ending one of my boyfriend's friendships and for making everyone else miserable at the same time. My boyfriend forgives me and constantly lets me know that he chose me and that things were better this way, but….I want to feel special to his parents. I may be selfish right now for wanting all of their attention I guess, but i've always felt like she was the other woman. I don't know how to act anymore….