Suggest Remedy For Frequent Urination

My 11 yrs old daughter is complaining of getting an urge to pass urine every 15-20 minutes for the past 1 week. She has recently travelled (about 10 days back) and did use a public toilet at the Airport. I suspect she has a mild UTI (although she has no pain or burning sensation) while passing urine. My wife gave her Alkason 1/2 tsp thrice a day for 3 days. However it initially helped slightly but the problem hasnt gone. Her school opens tomorrow and she does not want to go to school because of the embarassment of asking to go to the toilet frequently. Can some safe generic antibiotic be administered till we get a urine test. being a Sunday I could not meet her Pediatrician.