My mom caught me smoking weed?

After school today me and my friends came over to my house to smoke some weed while my mom and brother where at work. We were in my room and didnt expect her till 5:00, but suddenly she walked in my room to ask me something and she saw me smoking it. I tried to play it off by hiding my hand behind my back but it didnt cut it. Then she yelled ''David!qu� es eso? iI said nothing and then she said ''por qu� haces esto a m� con usted mehito?! and then she made my friends leave and i havent talked to her or been out of my room since? How can i make her forgive me?:(