Can you help me think of an idea to see this guy saturday?

this guy ive known for 7/8 months is leaving the city on sunday so saturday is my last day to see him. my mum recently read my diary and found out some bad things ive been doin, smokin pot gettin pissed etc so she doesnt trust me as much anymore. i can understand how she feels though and ive done my best up to this date to try gain it back, ive got involved in family activities and helped her out and stuff like helpin to make tea... thing is i wanna sleep out saturday. its not only me and him theres loadsa other people and its like a leavin party thing but how can i get out? my mum wouldnt want me sleepin at a boys do you think she'll understand if i say theres other people there too? i dont want to lie because ive lied to her enough in the past and i want to stop!! (hope that makes sense!)