Why is it so hard to keep a friend as a mother?

My feelings are hurt because I had a close friend that has been around my kids, a person that I made the godmother of my kids felt like I wasn’t a good enough friend for her because I couldn’t make the time to answer her phone calls or text back or simply just sit on the phone and listen to her gossip about her man problems or messy situations that she has had with females. Mind you, I am a mother of two under two (22 month old and a almost 5 month old) I cannot and will not put my kids last and miss out on them to listen to unserious drama from a immature 28 year old woman. My feelings are hurt because I had this woman around my kids and she was so quick to end the friendship over a misunderstanding, but allows males that are no good for her as well as females that are no good for her to continue to be in and out of her life and treat her like crap. Never genuinely checked on me during my pregnancy or after, didn’t get me a gift like I did for her on her birthday (it was small and very thoughtful) didn’t even get her god daughter anything for her arrival. I understand that I will never be friends this person because I don’t allow people to be in and out of my life as well as my children’s. Why is it so hard for mothers to keep friends or even make friends?