When should I let my baby go around dads new girlfriend?

So, long story short- my baby’s dad and I weren’t necessarily in a “relationship” when I conceived. We had been a thing off and on for about 5-6 months and decided to be exclusive but for whatever immature reason he didn’t want to be in a relationship yet. Yeah I know, I was stupid for allowing that.

Fast forward- one month after I found out I was pregnant he started dating some new girl. That was hurtful enough. But whatever, he promised that she wouldn’t get in the way of his support of the pregnancy and his child.

Fast forward again- around 33 weeks pregnant he decides he doesn’t want anything to do with the baby until there’s a dna test. Again, hurtful. But I couldn’t change his mind. He was partying in Mexico when I was giving birth. And didn’t meet her until we got the results at 3 months old. For obvious reasons I have hard feelings against him and the girl he ran off with. She knew I was pregnant and saw nothing wrong with him disregarding everything.

Fast forward one last time- he has been great with her. Shows that he truly wants to be a good dad. I feel like while my baby is young we need to both bond with her together. He always wants to take her places without me or take her around his girlfriend. (Who has been extremely disrespectful towards me)

And I just don’t find it necessary? Of course when she’s older, it’s inevitable...but she’s still just ababy (4 months) and I see no reason for her to be around the girlfriend? I just need time to heal, and it’s not that I’m letting my need for healing getting in the way of the child/father relationship...I just don’t see the need for the girlfriend to be involved quite yet.