Even if one of them is the sperm donor/vendor.
She is complicit in denying her child the right to his own mother and his natural kin: the first right a child has after the right to life itself.
And on a more heart-felt level: isn't the anxiety going to torment her for the rest of her life? What th' hell does she think she's doing?
When the two guys break up, is she going to reappear to reclaim the child?
I suppose they'll go on to adopt a second child, so they can each have one.
The biological mother might simply have sold her eggs to a broker, while the gestational carrier was contracted separately.