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IM sorry to hear about Tabithas recent troubles. It sounds like she may have developed an ear infection. This is a common cause of sensitive ears and shaking her head. The infection may be in her outer, inner or middle ear and she should have an otoscopic exam by your veterinarian to determine the cause of her sensitivity.
Other causes of ear sensitivity and shaking her head include a polyp (benign growth in the ear), mites (less likely if she is indoor only, or simply that you are stimulating her natural reflex to twitch her ear. This usually does not cause head shaking though so you are right to be concerned. I recommend taking her to your vet for an exam at your earliest convenience.
Was I able to answer your questions tonight?
You can try to clean her ears out with an over the counter ear cleaner, however without an exam I cannot tell you the state of her ears and if her ear drum is intact. You can use a dilute vinegar solution (wet a cotton ball and gently wipe the inside of her ear) as well and if this helps then you can continue to monitor her but ultimately, if the issue continues and you are concerned about her, then she will beed to be examined to know what is wrong.