My girlfriend is too fucking annoying

I've been with my girlfriend a year and a half and sometimes I feel like I'm dating a High school girl. She's so needy and doesn't understand I have responsibilities. My son is 15 with a heart condition. He's had 4 open heart surgeries just this YEAR! She will blow up my phone during his surgery just to complain to me about stuff. I have no problem with her complaining to me but she only wants to do this when I'm with my son or at his doctors appointments or surgeries. If we are together she plays on her phone. If I try to talk to her about it she just posts on Facebook that I'm a neglectful boyfriend who never wants to spend time with her. Why does she only want to spend time with me when I'm with my son. Then she's getting into it with my son's mom for no reason. She's an extremely unproblematic person so Idk why my girlfriend feels the need to start shit with her. She started a fight with her once because she brought our son McDonald's and my son shared with.me.so my girlfriend went off on my baby mama saying the only reason she bought my son McDonald's was to get me McDonald's

I tried breaking up.with her 3 separate times and she threatened to kill herself!