AIO: New BF is “best friends” with a woman he used to sleep with

I’ll keep this as short as possible. I’ve been dating my boyfriend for about seven months and he has this so-called best friend. They don’t see each other, they don’t really hang out. They just talk on the phone from what I know. She’s always trying to get him to hang out, but I tell him with their pass. I don’t feel comfortable with that. He told me that she is a woman that he didn’t wanna be with, but she didn’t wanna be with him

When I first met him, she came over to his house one day when I was there, and I spoke to her, and she was very rude to me and from that point, I just didn’t like her. She apologized and said that it had something to do with an issue they had going on, but my question was why be rude to me?

Fast-forward to last week, she asked him to go out and again I wasn’t comfortable with it and I asked him well since she has a boyfriend too. Why don’t we all go on a double date ? He said he would ask her and he did. He was talking to her today and she said that a double date would never happen. That she’s gonna keep her private life to herself or something like that but she just wouldn’t do it. I think that’s weird because you have a boyfriend he has a girlfriend. Why do you always try to get to hang out with my boyfriend alone? She’s doing this guilt trip thing on him where she’s saying that she feels like I’m taking him from her.

If I felt uncomfortable for, I’m definitely uneasy about their relationship now. Am I overreacting or could it be as innocent as they say?