Good news: We were given $1000 by United for the trouble.

Apart from the stress on my wife, it all worked out well. We were able to rebook her flight two days later for huge discount over what we had paid initially (88k miles versus 175k miles), she and the baby were able to celebrate the Solstice with her family (they had a great time), and we got $1000 in travel credits that we can use however we want. Ultimately, she faced no professional consequences, either.

1KVoice took a while to respond but when they did, I was satisfied, and my wife will no longer make the mistake of not adding the baby when she makes the initial booking.

Thanks to all of you for your encouragement and advice - especially to email 1kvoice directly. Very helpful.