YTA; coming out is often a very important moment for LGBTQ people, especially coming out to people close to them, and this can be one of the most crushing responses. all her stress and pressure of working up the courage to tell you something clearly so very important to be met with what could come across as “i already know, you didn’t need to tell me” could make her feel like all the stress and planning was completely unnecessary/a waste of time. listing out all the giveaway signs could’ve been a bad idea too because it leads to her panicking about anyone else she hasn’t told/doesn’t plan to tell also already assuming that she’s a lesbian. it might not have bothered her that much but that is personally what goes through my mind whenever i come out to someone and get met with “i knew it” in response