why the rush?
Ok, first off, my thoughts are kinda like "Why ruin a good thing by going too fast?" You guys all love each other and are serious about having a triad based on equality, I get that. Obviously, with rings and a new vehicle, this is following a somewhat "family" dynamic, and what's more "family" then babies... except, when one partner isn't ready.
Let's think about this from a couple dynamic to help take out the poly element. If a man and a woman were together and the woman wanted a baby but the man didn't yet, would it be okay for her to secretly schedule their sex around her ovulation time? If he said he wanted babies, just not yet, why wouldn't she trust him? Thinking about it like that might help you to figure out some of the questions you'd like to ask her/them.
So many questions here jump out at me...
1. Is there a specific reason why she feels the baby has to be now? ie maybe there's some underlying worry that she's getting too old to have a baby? Or is it insecurity that she feels she needs the validation that she "really is an equal"?
2. The child would be just as much YOUR child as her child... so of course you should have a say. I think sitting down with HER and talking about "when do WE want to have a child" ie as the woman that you're in love with and want to be with for the rest of your life, when do you see making a baby with her makes sense to you both? Making that decision just like you would with a lesbian partner who needs the consent of the sperm donor is another way of looking at it. AFter all, you love her, and are committed to her. So having some real, honest, deep conversation about "this isn't about me stopping you, this is about me exploring what we want in my romantic relationship WITH YOU" is important.
Best of luck!