Do you need long shorts even if you are a girl?

Yep - but most of the time you'll be wearing a Sulu (like a sarong/skirt) anyway, especially in the villages. When you aren't in the villages it isn't a big deal so you can basically wear what you like but at least one pair of long-ish shorts, like hiking shorts are a fantastic idea!

I wore Nike shorts the whole time and I was fine! the only thing too keep in mind is that you should pack more tshirts and less tanktops.

Yes and no. You need a long skirt (not long pants) to go to some villages. Most of the time I was fine in the shorts that are short aside from the villages