OP..
First off, you are a grown a-- man and don't have to explain your actions to anyone including your girl!
Your girl's mom's homegirl was out of line questioning you about your life. What you got going on in your life is YOUR business!
You are correct, that woman was disrespectful and you didn't want to act out of character so you left...
As for your girl, seems like there is something going on with her because instead of her being concerned about how you felt, she prioritized her feelings without understanding the whole situation.
Tbh..
If your girl is gonna get weird on you taking about needing to put her guard up and all that nonsense over a situation like this, then it seems to me that she is already preparing herself to get out of your life in the foreseeable future.
If it was me, I would tell her that I don't take kindly to idle threats. If she wanna play mind games and get fake mad over iish that had nothing to do with her and not care about how I feel about things, then she need to leave and go on about her life.
Man, life is too short to put up with emotionally immature ppl. Also, you are a Dad who has custody of your child and that is your #1 priority. Anyone who has a problem with it can kick rocks!
Don't let any woman talk to you crazy! Never compromise with respect! A woman who genuinely care about you would give you grace and attempt to be understanding of your situation and feelings. Keep that in mind as you move forward in your relationship..