<human>: Can you succinctly summarize the text in 1-3 sentences?

A little background: my brother and his gf, Brittany, were together for 2 years. The day I had my son, they actually officially got together. He was living with me and then jumped into living with her. Things went swimmingly until 10 months into their lease, her parents offered for her to move back in with them. She accepted and told my brother, Michael, he should ask to move back in with me....on 4 days notice. I, of course, accepted...on some conditions, that he be available to nanny for me while I work and go back to school and I wont charge rent.

Fast forward 8-9mos later, I'm in the middle of interning when I get a text from Brittany. We hadn't talked for months at that point as we had kind of drifted from being friends. The text read, "Michael talked to you last night about not babysitting. What do we do with your son?" Confused, I called Michael to ask what Brittany was talking about. I was on the phone for an hour when the conversation devolved into Brittany chastising me for not having a backup babysitter and basically calling me a neglectful mother to the point where she felt she should call CPS on me. I banned her from my home and seriously talked to Michael about his girlfriend's actions. He didn't know why she lashed out again me and would not back her up on her accusations. 

So, now in the present:  it's been 2 months since the blowout and I've come to find out through Michael's friends that Brittany is now the ex girlfriend. Last night we were all drinking together when his friend started in on Brittany. I stayed backseat in the conversation until Michael mentioned that she called him out of the blue and started asking about my son, how he's doing in daycare and that she wanted a picture so she knew he was okay. My brother flipped when I flipped out saying, "I should've never told you! You're trying to start drama!" He's since apologized but I'm still on the verge of contacting her and threatening legal action if she doesn't leave me and son alone. 

Reddit, what do I do?
<bot>: brother's psychotic ex is fixated on my son and I'm trying not to fuck her face up....what do?