Best friends of 20 years- are we drifting apart

So this is a bit of a long one. I have been friends with let’s call her Sammy, for 20 years- since the first year of high school. We have done so much together, holidays, millions of nights out, travelled to Australia and I was maid of honour at her wedding. So we have recently both had baby girls, she had her baby 3 months before me. When we were pregnant we talked about maternity leave and how we would spend all this time together and do all these lovely things. So like I said Sammy had her baby 3 months before I had mine. She met some girls and they started hanging out a lot. I just kind of assumed that when I had my baby I would just start hanging with them too, why wouldn’t I , that’s my best friend. However, when I had my girl and started mentioning coming along to things, I noticed a kind of resistance from my friend-as if she didn’t want me to. She never said anything but she never once invited me- even when she knew I was free, she never really encouraged me to come along to anything they were organising. I’m not going to lie it really upset me. I tried to meet people and did meet with a few mums but I haven’t really got close with anyone. Now months later, Sammy invites me to things with them but it’s super awkward because they all have a super close bond and I just feel

Like the weird tag along- and her friends don’t speak to me, sometimes they don’t even look in my direction. I am happy for her in some ways but I just feel sad that she has the new circle of friends and spends all this time with them and I just feel like an outsider. I don’t want to come across bitter or jealous- I really am just sad about the whole thing. I guess my question is, do I bring this up to her, or do I just leave it and see what happens?