I think nitrofurantoin is necessary. Let me explain.
Urinary tract infection is very common in the elderly women, and E. coli is probably the most common pathogen for UTI. For elderly women, the main conundrum for the treatment of UTI is the risk of relapse/recurrence. Basically, even if you eradicate the pathogen by antibiotics, and discontinue the antibiotics, the UTI will still come again in the majority of cases. Thus, for the treatment of UTI in elderly women, continuous oral antibiotics are essential in preventing another attack. Of all the antibiotics, nitrofurantoin is the best candidate, and it is probably the only antibiotic that can be used for a long-time for UTI prevention. You mentioned that it is not good for people >65. May I ask what is exactly bad?