I'm sorry Zoe isn't feeling well.
Because you were away for 2 weeks, it's difficult for you to guess (and for me to guess) at what's causing Zoe's discomfort. Do you see her going into the litterbox frequently, straining to urinate and then nothing happens? That would be a sign of a UTI
She may not have eaten properly because she missed you and/or she may not have gotten her methimazole every day, while you were away, so due to her advanced age, current medical conditions and symptoms she's exhibiting, I'd advise you to bring her to the ER vet. I realize it's expensive, too, but if you apply for Care Credit, you might not have to pay anything tonight. It's a credit card for human health, dental, veterinary services, etc. Some plans may even have no interest for a short while, then you start making installment payments. Here's more information about Care Credit:
I hope all will be well with Zoe and please let me know how she's doing and what the vet's findings are. Thanks!
Please be so kind as to rate my answer with positive feedback, as that is the only way I receive recognition from the website for my assistance. Thank you very much!
Providing a positive rating will not end our conversation, should you need me for any follow-up. Simply click 'Reply to Expert' for clarification or additional information, if needed.