I am looking for advise about how to respond to an old friend who just posted on Facebook that she is engaged to a woman. I'm very happy for my friend, but was unaware she was gay (we lost touch three years ago after being close friends throughout high school and college). I messaged her best wishes and a few personal remarks and she responded with thanks, saying it has been forever since we talked and she apologized for not telling me she was gay.
My question is (if we start to reconnect): should I bring up her orientation or let her bring it up. I don't want her to feel like she needs to explain herself, but I also don't want her to think I'm ignoring it.
I'm sorry for my ignorance, but I do not want to offend my friend, so I hope you don't mind me asking for advice from people who may have a better understanding of her feelings than me.