d-mannose is correct. It is actually the constituent part of cranberry juice that makes a difference, however it is orders of magnitude more concentrated when taken as a powder (mixed in cranberry juice or other liquid).

However, be aware that it only works on e-coli based UTI and if the infectious e-coli pathogen does not have mutated type fimbriae. It is notable that somewhere between 80% and 90+% of all UTIs are indeed E-coli based and only a very small fraction of these E-coli based infections involve mutated fimbriae. If she has mutated e-coli or some other non e-coli based infection then antibiotics will likely be required. A lab test will show whether the infection is e-coli. In any event, d-mannose has been shown to be safe so there is no risk in giving it. When the infection is e-coli based you will see benefits almost immediately in the context of reduced pain. d-mannose prevents adhesion of non-mutated e-coli to epithelial cells and without adhesion (binding) the would-be infectious bacteria get flushed away in the regular urine output.

Please follow Trinity's advice if not the above and get a tele-doctor quickly. UTI must be treated quickly! Suggest a Naturopathic doctor if one is available locally as well.

Godspeed!