I do know that high blood pressure (medical term is "hypertension") can cause excessive vocalization in cats. See link below that mentions this (and within the article is a link to "hypertension" - click on the word to take you there). Elevated blood pressure is common in older cats, due to things like kidney disease (CRF) and hyperthyroidism. You mention your cat seems to forget she's eaten; although she's tested negative for hyperT in the past, from what I understand a cat may still be Hyperthyroid but basic bloodtests for same are NEGATIVE.
How is your cat's vision? How old is she?
Does she seem to bump into things? Do her eyes appear cloudy? (cats often get cataracts like humans do, which causes eye to appear cloudy). If a cat isn't seeing all that well, particularly at night when the lights in the house are generally turned off (it's a myth that cats can see it total darkness), perhaps she's vocal because she's feeling somewhat "lost" in the darkness or because she can't see as well? Can you leave some lights on in the house? And some nightlights?
Also, untreated high blood pressure can put a cat at risk for developing detached retinas in the eye...........which can then lead to blindness.
I would definitely suggest asking your Vet to check kitty's blood pressure. Several readings are best......if you take the first reading, it can naturally be elevated, just like in humans at the doctor's office, just due to the stress of being at the Vet.
How does kitty's hearing seem to you? I have one cat, adopted her as a stray many years ago (in 97). She's at least 14 yrs old. About a couple years ago I noticed she was deaf! She used to always come when I'd call her but that no longer was the case. And if she was in the same room and I said her name, even very very loudly, she wouldn't hear it. I have to absolutely HOLLER for her to hear "something" .....and even then she doesn't seem to be able to discern "where" the noise is coming from, just that she heard "something." It's possible she's a lot older than 14. Vet checked her ears, nothing wrong with them, he suspected she was deaf. Even if I clap my hands right next to her head she doesn't startle. Not sure if there's any correlation but I seemed to notice this a couple months after she had a dental 2 years ago. I did read once that anesthetic can cause deafness, can't remember where I read it. And some meds can cause "ototoxicity" (causes deafness).
She will often start crying out.........almost like she's lost. She used to do this a few years ago and when she'd "see me" she'd stop. Perhaps it was the start of her losing her hearing? Sometimes she'll do it for 5 minutes straight, during the day...........sometimes at night (I always keep a few lights on in my house during the night) and I'll have to see her to get her to stop because calling her no longer stops her from doing this.
Because she's deaf, now when I get home from work, my 4 other cats will hear me and they'll come to see me........and I feed them. I have to go upstairs to my room where she hangs out during the day and "get her" and bring her downstairs or else she will have no idea I'm home and that it's feeding time.
http://www.sniksnak.com/cathealth/vocalization.html