you got caught with an empty jar. you didnt get caught with/smoking weed

you're still in a good position to deny deny deny. but, if you want, the contrition card is still in play as well. apologize profusely, talk about how it wasnt enjoyable and how you regret even doing it in the first place. i dont fucking know man, just convey an overall sense of contrition. fuck you can even blame it on a girl you met and got swept up and pressured into smoking because you like her. you've literally got the world at your fingertips with stories and excuses if this is the position you want to take. it'll probably be the easiest one for your aunt to digest anyway unless you have a long history of this stuff

if you have to confess to something just blame it on being in a new town and bored and restless yada yada

i wouldn't go the "its my life, i do what the fuck i want, im not hurting anyone etc..." route just yet. you may be able to escape this unscathed and dont want to rat yourself out even more if its not necessary