Tell her to stop the cranberry juice and everything acidic and/or sweet. Avoid all juice, soda, alcohol, coffee, tea, etc. Cranberry juice is actually hard on the kidneys and can aggravate interstitial cystitis.

Cut out everything spicy, too.

Have her get some urine pH test strips. They have to be for urine, not just the average ones (not accurate enough).

She may discover that her urine is acidic. Take a teaspoon of baking soda in a shot of water and test again in half an hour. Do this to keep urine in the neutral range. Once the symptoms subside she can reintroduce non-sugary acidic drinks; and may wish to neutralize them with a pinch of baking soda.

Also, make sure that she is treating for Candida. Yeast infections from antibiotics can mimic the symptoms of UTI.

I manage my chronic UTIs/IC with these methods. Hope that she gets better!