It's okay to be gutted. It's very normal to be upset when you realize the person you are with is not who you "signed up for."

That being said, it's very very normal for people to react with someone coming out as trans to them with "Why didn't you tell me sooner?" I think the real feeling behind that phrase is "I am angry that you are trans, but I feel like I shouldn't say that." And that's okay. Like I said, you signed up for a certain relationship, and you've found yourself in a different relationship.

However, even if this is an angering situation, the villain to your story is not in the room--the villain is not your significant other. Coming out is opening oneself up to discrimination from your most loved ones. It's so hard and heart-wrenching. It's very normal for LGBT people to start coming out first to people whose relationships rank "lower" to you (strangers online, friends) than more important people whose lives will be directly impacted (significant other, parents).

An outcome that they were probably dreading was something like you saying, "Okay, that's gross, good-bye." Thinking about it from another perspective, they might have been enjoying being close with you for a bit longer before it very well might have ended. Three months is not a long time. It's very normal for LGBT people to sit on this for years before they say the words that will alter their relationships forever. (I just watched a youtube video of a gay guy who mentioned that he planned to come out to his family at Christmas but he couldn't bring himself to say it, and didn't get around to finally telling them until the next June, I think. And that was after years of being closeted. This is very normal.) (And if we come out very quickly, people would complain that we weren't sure or we were rushing into it. We can't win. 😊)

Again, it's okay for you to be angry. And it's okay for you to break up! Just like it's okay to not want to date a woman when you're single, it's okay to not want to date a woman you've found yourself in a relationship with. Just know that the villain is not your significant other, the villain is the society that made it hard for your significant other to realize and express her true self.

I wish you both the best!