BH just popped in, so I've asked him.
First question same as mine!
Then he said he'd be worried that the pelvis would never have been loosened up on the one, and would have stiffened up on the other, and so there might be a risk of needing a caesarean.
Also, the one that's never been in calf has no experience of feeding a calf, so might need help getting used to that. If she's not very tame, and/or you don't have good facilities, that might be an issue.
He personally wouldn't risk it, he says; too likely to be a downside.