The orange color could simply be normal. Often when urine sits for a while and oxidizes, it becomes an orange/brown color. OTOH, it could be the result of something she ate, but I've never seen my cavy's urine change color from anything he has ingested. And, yes, it could be a UTI.
If she exhibits any straining, hunching, crying when she urinates, then get her to a vet ASAP. As you probably know, a UTI is painful and needs to receive prompt treatment.