L.A.
I am wondering 2 things. Is it possible your friend has always been preoccupied with herself all of these years? Or have you changed and are not willing to put up with her anymore?
As we mature, we begin to see things more clearly. New things begin to take on more importance. Being a mother is your priority. Some people with children do not feel the same when they have children. You and I cannot understand this, but some people just treat it differently.
We cannot say if this is good or bad, because we do not live their lives. We cannot judge, because we cannot know what is in their hearts.
I do not know about you, but a long time ago I realized that there are tons of wonderful people in my life and even more I have not met. I do not have time for childish behavior. I also do not have time or energy for negative people in my life (includes family members). I do not want my child to be around grown ups like this, so I have excused myself from their company and am very fortunate to have wonderful friends.
You cannot always avoid these people, especially family, but you can be polite and not engage them or be pulled into their shenanigans.
Also always try to treat people the way you want them to treat your child. If your child is having a bad day, give her a break. If she is always selfish, tell her you are disappointed and know she can do better. Your friend sounds like she has not been told her behavior disappoints you. You may need to tell her you need a break until she can treat you with respect.
Also take a look at your friend. Does she seem to have changed a lot? Could she be having emotional problems? Is there something going on that has changed her, besides motherhood? She may need to get a check up and make sure she is not having emotional problems.