Your real problem isn't where your D is going to be living & how she will be raised. Your real problem is that your girlfriend is asking something totally unreasonable of you & refuses to consider any option or even to agree to get a neutral party to help you guys sort this out. Because that means if you give in to her now, that is how she will keep bullying you into allowing her to call all the shots.
What sort of a relationship is that? Certainly not one that is a good healthy one for either of you. So in the long run, you will have traumatized your young D by having her uprooted & probably still end up with the girlfriend leaving or making life impossible for you as well as your D.
Many women have young children to care for while they are pg & manage to be more compassionate then she is being, even if the child is not biologically thiers. This is a power & control issue for her, which involves a major impact on a very young child that needs her daddy's love & stability in her life. This is not about you bringing your girlfriend ice cream & doing the laundry to make her pg easier.
You need to decide how much you are willing to give up to please someone that isn't willing to see your side of the issue at all but wants only her selfishness & short sightedness appeased no matter at what cost. If you give in now, where will you draw the line & say "This relationship needs to be a 2 way street & that means we have to work together to reach reasonable solutions to our issues"? You will be teaching her to treat you very badly & it's doubtful she will treat your D or son much better, selfish people generally do not make good parents to their own or other kids.
You will need some professional help to get your relationship on the right track. Schedule an appt with someone, check them out & then invite her to attend. If she refuses to go or to constructively talk this out with someone that can be an intermediary, that will let you know that any issues you have with her are going to be impossible to resolve constructively, big or small. Meaning unless you are willing to put up with that, this relationship doesn't have much chance of success or longevity, unfortunately.

