How long does it take to build muscle?

So im a 14 year old girl and i want to gain some upper body strength. The main reasons are:

1. I go to a lot of hard rock and punk concerts and i want to be able to push people away from me.

2. Im in a rock band and im the only girl so for me to play with boys, i have to pick up my instrument equipment. Which is a heavy bass amp.

3. Just in general to stay fit. :D

I also want to lose a little tummy flab, i dont want rock hard abs but i gained like 7lbs because of thanksgiving and other recent holidays :(

I run after school a little bit to music

My only problem is i have a very busy schedule. I only have time for about 10-20 minutes in the morning for 5 days a week. I also eat pretty healthy.

Any help/advice? Please and thank you so much

BQ: some dude told me, girls cant gain muscle in a short period of time like guys can. Is this true?

BQ: Any other foods i should eat to help build muscle?

BQ: whats your favorite kind of music?