Girlfriends texting ex everyday all day

So my girlfriend who I’ve been with for about two years has a child with her ex witch I’m fine with I have other kids from a previous relationship as well. But there texting each other on a consistently through out the day about her kid. That’s not ok with me and I’ve spoken to her a few times about it but she seems to not get it it nothing to talk about all day every day. I love her but if she can’t fix it then I’m going to have to do something. What’s your thoughts on how to fix it