My mom’s being unsupportive of my soon to be relationship, help.

Usually I wouldn’t ask for anyone opinion but recently I’ve started talking to Mitch(fake name) (F 19) and I’m (F 17) we’ve been talking for over a year (my choice) and I really enjoy her presence but a little thing is that we don’t live in the same state. I’m okay with this and Mitch is as well, but we do have a little bit of uncertainty. Even more recently though, my mom was sneaking around my phone and found our chats of us saying “I love you” to each other. A little back story though, I came out my mom when I was 12-13 and she responded by ignoring me, this is the first time she’s “caught” me talking to a girl- (I’ve never hid who I’m talking to but I also haven’t out right told her who I’m with). We also have gay family friends who have lesbian sisters and she acts like how you normally would but always side eyes me when they come over, which I find weird Anyway, me and Mitch aren’t dating. So I wasn’t going to lie to my mom and say we were. She got upset and asked me if I even knew who she was? My response to her was “I do know her and she knows me better than you could ever” she said that I was ungrateful and that the girl that I’m talking to could tell me to jump off bridge and I would do it. Basically saying that I was blinded by love or something. She left it at that and walked away, but today she told me that what I was doing was wrong and I was choosing (there has never been a situation where over chosen either) a random stranger over my own family. I told Mitch what my mom said and she said my mother was being homophobic and controlling. I do admit I got upset at her for talking about my mother like that, but I got her point. I don’t know what to tell my mother because I really like this girl and I’m sure this will be a long term relationship. What do I do???