Firstly, OP. Well done for coming on here and asking for advice.
I'm going to give a different perspective here (and I could be completely wrong). Because option 1 is that she showed you from the beginning who she was, that she wasn't great with your DC and, despite that, you both had a baby (congrats on your baby btw).
Option 2 however (and I speak from experience here), is if you live and breathe for your DC, they're the only thing that keep you on the straight and narrow and you see them every weekend (from Friday until Sunday), where does that leave space for your DP?
My exDP is currently an ex for precisely that reason and we are working on trying to find a way forward. He too lives for his DC, he has been consumed (for years) fighting for progression of contact from where it is. Entirely admirable and I respect that. BUT, do you have any idea what it feels like to be in a relationship where someone is so laser focussed on their DC only? Where every decision is dictated by what his DC need? It's like being a second class citizen, permanently.
I once said to him that it felt like he existed with me week to week and that he only lived for when he saw his DC. I'm telling you now, it's a horrible place to be - mentally and emotionally and it took me months upon months to figure out why I was struggling.
He too was consumed with guilt, so when he wasn't with his dc, it was like living with someone who had a permanent 'heaviness' about him.
I am telling you now, it made me miserable.
He too wanted a baby with me and more than anything I am so so so glad that I refused. Your partner has just had your baby and as opposed to supporting her, and enjoying YOUR new baby, you're crying over the children you don't have with you, consumed with your guilt.
I know she could just not be a very nice person, but right now, my heart goes out to her. I could have been her and my DP would have been just as self involved and one sided as you are (potentially) being.