She’s eating some and she sounds stable so I don’t think you have an emergency on your hands. If I were you, I’d be calling around to find an internist who can see her next week — then tell your regular vet where to send the records, radiographs, and recent bloodwork. Of course, if something changes or you think she’s not stable then just take her to an emergency hospital at any time (preferably one with an Internal Medicine department). You don’t need any records in hand to do that, although it may save you some expense if you have recent bloodwork so they don’t have to repeat it. If you call around a bunch of places and find no one can schedule you until a month from now, your two options are to have your vet contact an internist and ask for an urgent appointment (though it doesn’t sound like he’s too concerned about your cat’s health status at the moment), or you can take her in through the emergency department and see if they will admit her and set you up with one of the internists for a next-day consult. Which, I imagine they will, if you tell them your cat has been inappetent for a few weeks, crying, hiding, generally dumpy, etc., it’s getting worse, and your vet can’t get to the bottom of it.
ETA: Some referral hospitals have specialists working on the weekends, or at least on Saturdays. Mine does. So, if you’re going to go the ER route of getting a consult, you could potentially take her in tonight to be seen tomorrow, but you need to call first and ask, “Do you have internists working on Saturday? If I brought my cat into the ER tonight and they determined she needed to be seen by IMED, would they be able to set her up with a consult tomorrow?” Don’t waste your money in the ER if you can’t get a consult, unless you actually have an emergency or are worried enough that you want someone to assess her. That’s an option, too — it doesn’t necessarily need to be an internist to figure out what’s wrong with her if an ER vet can see something your vet hasn’t.