NTA. The one on ones, wearing hoodies, pushing boundaries. I’m not sure why she can’t respect your relationship. Just from the one on ones, she doesn’t want you in the picture. Which doesn’t make sense. If they are truly that good of friends, I’d imagine she’d want to hang out with both of you, and get to know his gf. Your insecurity is valid when it comes to Amanda.

Have a talk with your bf about setting boundaries, and discuss what specific events are making you insecure. If you want, reach out to Amanda in friendly terms. Try to be her friend. If she’s not open to that, she clearly has ulterior motives. If she receives friendship well, then there’s no reason to worry and you can all hang out!