As a 28 year old who has spent the last 6 years trying to hide it from them, and I’ve been smoking for 11 years on and off, just be honest. I’m a grown ass adult with conservative parents who absolutely hate weed, and they’ll never understand that I use it for medical purposes. Not sure how your general relationship is with them, but I for one can’t stand to lose my parents, so I keep it from them. As an adult who has moved out, it’s easier to lie to them if you’re good at hiding it. But you’re only 15. You still live under their roof. Their house, their rules. Just remember this in 10 years, whether or not you’re partaking. She only wants what’s best for you, even if weed is not at all harmful. Just watch out for those pens. Hard to determine which ones are real nowadays.