Can I marry my girlfriend as soon as she turns 18? She will still be in high school for four months.?

My girlfriend's dad hates me. We want to get married as soon as she turns 18. She will still have 4 months of high school left. I was planning to tell them before, but due to unforeseen circumstances I can't anymore. I was wondering if we go to her house that day and just spring it on them basically saying, "Hi, sorry she didn't come home right afterschool we got married. We're here to pick up her things. She's moving in with me." Could they stop us or sue me or anything? I live in California. Don't tell me all that crap about being too young to marry please.