Need help with parental issues?

im 20 yrs old and i am currently livin with my mom due to no room mate situation. she caught me smokin weed and is all freakin out and threatining to send me to rehab. my question is now that i am over 18 does she have any control over me legaly? can she send me to rehab against my will? and if i move out can she do anything to detain me or keep me at the house legally?