I'm sure you would have felt her on the head of your penis had it actually been exposed. For that reason, we are going to assume it wasn't actually exposed.
That means the answer to all your questions is no, you had no risk for anything. No STD, including HIV, goes through clothing.
HIV, chlamydia, gonorrhea, mycoplasma, trich, and the hep viruses require penetration to transmit. You didn't have that, so even if it was sticking out, you have no risk.
Herpes, HPV and syphilis require only skin to skin contact, but also require friction, usually the kind associated with intercourse. It doesn't sound like that happened, so even if there was direct contact with her vagina, you're fine.
Wouldn't worry about a thing.