He said/She said but who's right?

Today's Ask a Bougie Chick comes from Donald and Cheri in Newark. Donald and his girlfriend of six months had a little contretemps and they want us to weigh in on who's right and who's wrong:

Hi Miss Michelle,
We've been dating long enough to call it exclusive but not long enough to have all the issues ironed out. Me (Donald) and my girl (Cheri) are single professionals in Newark. I work in Manhattan, she works in Jersey City. We kinda live together. Like she has her own spot but she's here all the time or most of it.

Not that it matters but I'm black and she's half-black and half Puerto Rican. Here's the deal, a few months ago my ex came by really late at night (after midnight). I was just going to ignore the door but she was texting and calling and could see a light on from outside. It was plain she wasn't going away. Cheri was like, just go open the door, tell her you are with somebody and shut it down. I went down and told her I had company. She went away.

A few nights ago, she came back. Again after midnight, same routine. This time Cheri is like, doesn't she know you have a girlfriend? Why is she here again? What is going on? Well I didn't tell her I had a girlfriend, I told her I had company last time so maybe she's just checking. Cheri goes to the door with a lot of attitude and long story short, they get into it screaming and shouting in the street and I have to step in between before things go from verbal to physical. After the ex leaves, Cheri wants to know why I didn't make it clear that I was in a relationship and she shouldn't come around and what was I going to do about it. I wanted to know why Cheri had to take it to a ghetto level.

I think she's wrong, she thinks I'm wrong. What do you think?

*exhales* Well, wow. First off, this letter is wrong for putting two L's in my name. Moving on. Next, I think of the A, B and C of you? You're all three wrong. Your ex is wrong for rolling up. It's hella-rude to drift by somebody's spot without calling first, particularly after 10:00pm. That's kinda hoodie, sir. 

Your girl is wrong for getting all up in it. She took a bad situation and made it worse. She could've taken the high road, after all, she was nestled up next to you, she already won.(Assuming you're a prize?) Anyway...

You were wrong for not breaking it down to the ex so it would be forever broke. When the relationship ends, so do the late night drive-by booty calls. Unless there's something else you'd like to share with the class? Your role as the one chick's ex and Cheri's new boo is to draw the boundaries and set the rules and make sure everybody adheres to them.

Ya'll all acting a little special. Chill needs to be achieved across the board. Good luck.

BnB - what say you? Who's right, who's wrong? How to avoid this? And have you been in this situation? If so, how did you handle? Do share...