How do u know when to let a friendship go (bestfriends) or keep trying ?

My bff and I never hang together out anymore. She has a boyfriend and every since then things have been going down hill. I EXPECT them to be around eachother a lot & stuff but any time we (as in me and her) are supposed to hang out she always invites him its always awkward because I'm quiet/shy and I always feel like I shouldn't be there like they'll be talkin and laughin about somethin that happened while they were hangin out and ill be just sittin there clueless. But anyway..she's about to have her baby I went to her baby shower which was my 1st time seeing her since she's been pregnant and she's 8 months. It was really awkward its like were fading away. What should I do? Let it go or try?