I am sorry that you have been waiting for a response. I recently just logged onto the site and noted that your question hasn't yet been answered. I am a licensed veterinarian with over 25 years’ experience and would be happy to work with you if you are still needing assistance.
It would be inappropriate to recommend antibiotics when we don't know if her symptoms are due to a bacterial infection and there is a good chance they aren't.
Cats can be affected by a condition called Feline Lower Urinary Tract Disease (FLUTD) which is the name given to a set of symptoms from various causes that can affect a cat's urinary system. The causes are varied and the age of the cat partly influences the likelihood of the cause. (ie older cats are more prone to bacterial infections than younger cats). Other common causes include bladder stones, crystals, tumors, and sometimes just inflammation from an unknown cause (more common in younger cats). Unfortunately, the all can show the same symptoms, no matter the cause and all are treated a little differently.
Unfortunately, there is nothing you have at home that will help. If it is a bacterial infection, she needs antibiotics, but it is very possible and likely that she doesn't. If it is a stone, it needs to be removed. It is possible that there are no bacteria at all and it is a problem called idiopathic cystitis. This is an inflammation without bacteria and for unknown reason. The good news is that many of these cats will improve on their own regardless of what treatment we provide. Usually we try to give them something for their discomfort until it resolves and make sure they don't obstruct. It is not uncommon for their symptoms to return again later and can come and go periodically throughout their life. Here is a great article about it and some of the ways we manage it: FIC
Unfortunately, without veterinary intervention and a physical exam as well as a urinalysis, it will be impossible to determine the appropriate treatment. Cranberry pills have not been shown to have any significant value. About all you can do for her on your own is to encourage increased water intake to help flush out the bladder. This can be done by watering down her food to make it as soupy as she will allow. Offering tuna juice or broth would work as well.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.