I agree with GuitarRox. I wouldn't worry about this at all.
This sounds like no risk to me. If her genital area did not touch yours directly, there was no 'skin to skin' contact. That doesn't mean skin to g string thong contact but genital to genital. This didn't happen, I'd not be concerned. Covered oral sex is also such that you were safe. I'd not be concerned about std's.