MPC; I understand your frustration. I once dated a girl that came to a first date w/ hiking shoes! NO! i did not indicate in any way that we were going mountain climbing or hiking.
I just realized she was a totally chilled out type, that wasn’t into the way she dressed at all and that it wasn’t for me.
Make sure to select a day and a time that is good for her,
so that she isn’t rushed or anything. Yeshivish girls DO NOT come on first two dates dressed casual. Especially not casual enough for you to be bothered by it.
If you mean wearing flats instead of heels, that’s normal, if you mean like wearing a sweatshirt, that’s not normal!
Is she’s nice looking 2u, then so what! take her to shoot some hoops or s/t, and when she ask you why, tell her you decide where to take the girl based on the way she’s dressed.
If she wants to go to a nice restaurant, she’ll get the hint.
Hatzlacha Rabboh!