I like #1, nice colours, good composition.
#2 is a good idea, but that thing in front of her left eye is distracting. Maybe moving in a bit closer to remove some of the clutter in front of her (some, not all) and the dead space over her.
#3 is a fun pose, but on my monitor, it looks like the white of her dress is blown out
#5 is a great shot, probably my fave of the set
#6 is a fun pic as well, but you cut off some feet and some of the person in the blue on the right
#7 great shot again. I would of liked to have her whole dress in the picture and again, the whites on my monitor in her dress seem blown out
Compositions are great, your point of view captures the essence of the sweet 15, although the photo i feel captures the essence of a sweet 15 is the image of the girl and her friends either dancing or skipping around? Shows the playfullness of a young 15 year old i feel. Also maybe its just that I'm on an uncalibrated monitor at the moment, but the white tones seem to be blown out in all the pictures. That would really be my only criticism. Looks great though other than that minor thing.
just a cultural note here: in mexico it is very common for a girls fifteenth birthday to be celebrated famously. from the looks of the subjects i would guess this is a family with hispanic heritage. so a big party for a girls 15th is not surprising.