I think you need other friends. As much as it may such for you, this is her FIRST boyfriend. She's going to be excited and want to spend a lot of time with her bf and for a lot of firsy timers there is a struggle with prioritizing friendships and romantic relationships at the same time. Just a learning curve you both have to get through
I don’t mean this rudely, but if you were truly happy for her don’t you think you wouldn’t secretly wish they would break up? If you were in her position don’t you think you’d be the same way? Idk maybe have a convo with her about hanging out and stuff. I always think about when my friends get married.. it’s just a natural part of growing up to not have as much time to spend with certain people. Just my take!