Your mate having friends of the opposite gender

So my boyfriend has this female friend. They've been friends way before me & him were even an item. She lived in Ohio but now she just moved to a city that's now 45 mins away from us w/ her new military husband. But lately all 3 of them has been hanging out. I'm not comfy w/ it because of my past experience but I just want to know am I trippin? It's like I know when a female secretly likes my boyfriend but the tricky part is that she has a husband. Any advice or stories w/ this situation?