Yes, but...
There is no evidence of "lunatic chick". And while it does seem she was "cheated on or getting dumped", she is also pregnant, presumably with his child (I realize that is a rebuttable presumption, per Maury Povich, but still). And with most southern states eliminating abortion rights, there are going to be a lot more discussions about the 18 years of child support obligations that states can impose after a simple DNA test.
So I'm not sure that a pregnant woman wanting to discuss options with the (presumed) father of the child is some sort of "lunatic" situation. And if the guy is on notice that his baby-mama is coming over to have a serious life-circumstances discussion, maybe HE is the "lunatic" to choose to be having a phone conversation with his new girl when he KNOWS a pregnant woman is showing up to talk to him.
He has a door with a lock. If she is a "lunatic", he doesn't have to let her in. I'm not taking anyone's side definitively, there was bad decision-making on the part of multiple individuals. And he is not 17, he's lived as an adult on his own for long enough to be aware that minor situations can escalate out-of-control if you don't use your head and work to prevent problems from arising.
I hope this situation is not permanently scarring for any/all parties, but Kirby has had a loooong history of problems over the past few years, and Colbie may bear the brunt of whatever reaction is coming next.