Just call her actual doctor. Seeing her in person here won't make a difference. If anything they'll send a script to a blood work place near for a urine test. She shows up, goes in a cup, and you both go on your way.

A bit annoying for females but it is what it is. If she's shy going in a public bathroom you can generally take the container home and do it there.

When the results come in your dr can prescribe the best antibiotic to your usual pharmacy.

Thats if they don't just give you a general antibiotic over the phone.

Just remember that she's a teenager and she's going to get upset easy so don't freak her out.