Since her infection sounds so serious it might not help, but it certainly won't hurt - go down and get some 100% cranberry juice (not the kind with sugar and ony a little juice) and it's a natural remedy for curing bacteria in the urinary tract and it also helps with pain. Also, make sure she isn't eating or drinking anything with sugar, high fructose corn syrup, etc. because the bacteria will only feed off of the sugar. It is so important that she is taking in fluids right now, not only a normal amount, but more than the usual amount. When my kids were sick they always used baby bottles - actually, they continued this until they were in 7th grade or so
It sounds strange, but if you can get her to drink more, this way, who cares!!
How long has she been on the antibiotics? It usually takes about 2 days to kick in, but no more than 3. If it has been 3 days or longer, then the antibiotic isn't working and she needs a different one. Did they do a culture (grow bacteria from her urine sample)? It takes a few days to grow the bacteria in a petri dish then they try different antibiotics to see which one the bacteria responds to best (kills it).