How does "Hey mum, I have a secret girlfriend" sound?

I'm just feeling particularly anxious right now and I need to let it out, and if anyone has some good advice, that's even better.

I tried to come out to my mum August of last year. She basically said "it's a phase, I don't think you're gay, you shouldn't tell anyone else" and that "I think you're just lonely and need a friend with common interests". In March, she met this lady who had a daughter who went to the same school as me. They compared kids (as parents do?) and turned out we had lots in common. I started talking to this girl, and long story short, she's my girlfriend now. Ironic, right? My family is totally aware of us being friends and my mum is thrilled that I'm actually leaving the house to do things with people, but she doesn't realize the nature of our relationship. At least I don't think so - I'm always a bit panicky about whether she (or my dad) found out somehow.

It's tearing me up keeping it a secret from them. It's not like they need to know the intimate details about who I'm dating, but being super paranoid when my girlfriend comes over isn't healthy. Plus, my girlfriend is headed to university next year without me (I'm a junior, she's technically taking a victory lap this year). If things keep going as they are, my relationship is going to become long-distance, and that's a pretty difficult thing to hide from your parents. Looming even closer is an annual Christmas party my family is having. My cousins bring their boyfriends/girlfriends sometimes, it's no big deal. It wouldn't be out of the ordinary for me to invite my "close friend" to come... But I think spending an evening without being able to hold her hand or anything would be worse than spending it without her.

Basically, right now having my parents not know is making me feel almost physically ill, but at the same time I have horrible anxiety about coming out. It's hard enough coping with my anxiety for regular things, multiply the normal anxiety of someone who wants to come out by that, and I feel like I'm going to explode. The idea of just telling them terrifies me, especially after what happened with my mum last summer. My parents have this thing, too, where if you want to talk about something serious they make it into a big deal, and I always end up crying. Giving them a letter or basically telling them any way but up-front, verbally, would have that effect. And I'm not just coming out to them, I'm telling them that the girl I've been hanging out with for months is actually my girlfriend. They never really established rules about dating, but I never dated anyone before, so I'm going into that part of it blind. At least they don't have to worry about me losing my innocence, because my girlfriend's parents are super religious and wouldn't even let us sleep in the same room together if the situation came up. (And they're the ones who are 100% okay with their gay daughter. Go figure.) My parents have probably figured out that she's gay, and if so they're okay with it, but the subject never came up, so I don't know that for sure. I almost wish they would catch us kissing or something so at least I didn't have to tell them...