My cat is acting unlike herself

Since January, I noticed her favoring her left paw. She specifically holds it up all while she’s sitting. I’ve seen her limp with the paw still held up once but otherwise she walks with it and lays on it without issue. Holding her paw up is unusual for her as that’s not been a habit for her past 6 years of life, until 2 months ago.

In addition to the paw favoring, she’s gotten chatty. She’s always been the silent type, minus purring and the brrrpt sound when she’s woken up from sleep. The meows had always been occasional, hard emphasis on occasional. Ever since January, I notice a major difference. She meows more frequently and generally makes a variety of sounds way more than previously.

The third unusual behavior that is increasingly worse is her level of aggression. She is the most polite cat I’ve ever met. Being aggressive is not her usual character. She is constantly lunging at and lashing out on my roommate’s dog. I chalked it up to her just disliking dogs, which is valid but she’s started to get aggressive with me too. Growling at me, hissing at me, even biting me and attacking me. It’s not constant behavior but it does sometimes happen and it’s shocking to me because she was never aggressive to me, ever, before the last 2 months. She even bit my roommate recently.

Another new thing happened tonight as well. She was in bed with me for sleep. I left the bed to go play games and she followed me, as she always does. She’s almost literally my shadow so her following me is like her to do so. But what wasn’t like her is that she left me alone, went to a completely different room and meowed nonstop. I came to check on her, she was behind a trash can (not stuck at all). Once she saw me, she stopped meowing. She looked at me, seemed to recognize me, made a little brrrrrpt sound, and ran towards me. If she weren’t only 6 years old, I would’ve been questioning if she has dementia.

I know I’m late to saying this but I have taken her to the vet in January. The vet checked her out and found nothing visible. No wounds, no sores, no weird growths going on. I had suggested maybe arthritis since she was declawed in the front two legs, but she’s only 6 years old so I don’t know if that’s a reasonable guess. The vet said to keep monitoring her. If I take her back to the vet, it might be for x ray (to see if her bones show signs of arthritis) but honestly I’m not confident I’ll get a clear answer.

I don’t know what’s wrong with her and it stresses me out. She’s a sweetheart and I know that her recent behavior is completely unlike her but I don’t have any clue what is causing her discomfort to make her act differently.