Maisie had a UTI - although that's slightly different from a bladder infection so I'm not sure how helpful this will be.
Yes, it is possible to have a UTI without crystals, or crystals without a UTI; they're actually separate problems. The reason they sometimes occur together is that the crystals may irritate the urethra and make it easier for bacteria to get in and take hold, but that isn't always the case.
Maisie was on a 14 day course of antibiotic, but he felt noticeably better within a day or two of starting it. Even if your cat seems better, you should always
give your pet all
of the antibiotic as prescribed even if she seems completely well again, or you can cause your pet to build up resistant bacteria in her system.
When you discover your cat is prone to urinary problems, it's important to make sure that he or she gets lots of moisture. Make sure clean water is available and changed at least daily; filtered water is better if possible because it has fewer minerals.
You should also get as much wet food into your pet's diet as you can, and aim for brands with plenty of protein and without much in the way of grain or vegetable ingredients, to help maintain urinary pH. My favourite brands are Before Grain, Wellness CORE, and EVO.
In terms of cost, the best value for me has been the large cans of EVO. (The 13.2 oz ones.) The product to package ratio is really good, and since each can lasts a couple of days the cost per serving is not that high.
It's also important to keep the litter box scooped at least daily, because you don't want your cat to hold in her urine, and a clean box encourages urination when she feels the urge.
For giving the antibiotics, I used Pill Pockets. They aren't expensive and they save so
much hassle! Basically it's a soft treat with a hole in it that you stick the pill in.
I know cat urinary problems are super stressful.
I've been there. Your kitty will be okay, though. It's treatable and manageable.
I hope your cat feels better soon!