I'd like to offer my advice, as An Alumna of ADPI from UNT...
A jean skirt will be more than appropriate. And yes, it will be hot, so be cute, but comfortable.
Does that help?
As for your weight, be yourself. Any chapter that cuts you because of weight isn't looking beyond superficial characteristics and isn't worth being a part of. You will find a home at UNT, but only if you are yourself 100%.
Good luck!
Any more questions to prepare you for next week??