I lied to my mom and I'm afraid

Okay so I'm 18, I'm graduating from high school in like a week, my friends and I decided to go camping as a senior skip day thing. I told my mom that the girls were staying out, but the boys had to leave by 10. My boyfriend, who I've been dating for a year and a half, and 2 other guys friends stayed the night out there. I feel awful that I lied, and everyone else told their parents that the boys were staying and they were fine with it, but I think mine would be angry. Am I awful? What should I do if she finds out?