13th girl BIrthday party ideas?!

Try having a music themed party...have an ipod-shaped and decorated cake...since ipods come in many colors have it be your favorite color, of course=D then have all of your guests dress up as their favorite singer or wear anything music related (band t-shirts) then you guys can all dance, play music video games-such as guitar hero, and have music style food/snacks...for example, you could make homemade pizza in the shape of a musical note or again, an ipod...then if they spend the night you could have cd's (aka: donuts lol) and peanut butter and jelly sandwiches on white and wheat bread with the crusts cut off then cut to look like piano keys when they are alternated...also you could have a bowl of dip in the middle of a plate surrounded by chips, pretzels, veggies, etc. to resemble a cd.
You could also have games (like the guitar hero contest, karaoke contests, best costume etc.) and give out inflatable instruments, cd's, or music sillybands as prizes.

I just had a party with an ipod cake=D

20 girls thats a party already mmm
jus have a little party at your house and order pizza and dance and have fun! you dont need a big party your only 13.

Orgy.

I would do a dance party! Invite the guys! Have fun!