Yep, just have an open and honest conversation with her, explaining your experience with stuttering and how that situation made you feel. It isn't a matter of you laying blame on her for what transpired with the baby conversation. I think her intentions were innocent and she didn't mean to embarrass you, but its important that you are honest and let her know how you feel, for the sake of a healthy relationship with her. If it was a situation where your girlfriend or anyone else you know, seemed to be intentionally putting you in a situation where they were trying to hear you stutter, like trying to trap you in a difficult speaking situation, that would be different. I think many people who stutter have difficulty speaking on command. I have difficulty reading aloud in front of a group, or repeating something that I just said, like if the person didn't hear me.