How do I do it ☹️ (sneaking out plan)

I turn 19 this year & have an obnoxiously controlling mother who gets too far into my dating life. She wants me to date this older man because he has money but I am in love with my best friend. We’ve been dating since early this year but kept it a secret so she wouldn’t try to keep us apart because she knows he’s liked me since we were 12. I’ve tried talking to her and coming out with my feelings towards him but she gets crazy, calls him ugly and insults him. Right now, he’s in Georgia for basic training. They’re having a family day event and his parents can’t go since they don’t have an ID, so he invited me. The day of the event is on August 17/18 but I’d have to leave on the 16th, come back on the 19th. I leave for college on August 20, which is 2 hours away from home. I told her about it, she went batshit crazy and told me no, that I have to be with this man who’s almost twice my age. Then I thought maybe I could say I was leaving for college already since I’m originally supposed to leave on the 14th, but then what am I gonna say when I come back. I really miss my bf & want to see him bad 😒 I’ll also feel bad since his parents aren’t going, I don’t want him to be alone while all his buddies are spending the day with their families. What can I do? There’s no way I can talk to her because she’s not having it