Im 14 and i drink and party on occasion, how do i tell my mom? because she is totally against it?

so im 14, turning 15 in june, and i started drinking last year. i go to parties on occasion, but not like every weekend or anything. i always have to stay the night at a friends so my parents dont find out. just today my mom said to me "do you hang around _______?" i said yes and she said 'well be carefull he drinks'. i feel like shed totally flip **** on me but i need to tell her eventually right??? HEELP <3