Thanks for the responses, everyone! Just to clarify, I'm fine with it and it's no biggie, but I figured she'd be struggling a bit with how (and when, and if) to tell co-workers and family, and shocked reactions, and then I thought many of you must have gone through this personally and know what it's like.
I've congratulated them both and they're very happy indeed
You could check out PFLAG. It might be helpful for you to understand your role in supporting her.