I’m so sorry you’re going through this. I’ve experienced very similar behaviors with an elderly cat, and here’s what worked for us:

1. We did take her to the vet and get a full senior panel done - as another commenter stated, the weight loss could be related to hyperthyroidism. Our cat was put first on oral medication, which was a nightmare to administer, and then an inner ear topical medication. Worked wonders! It’s compounded, so it’s expensive, but with her hyperthyroidism managed, she lived 3 more very happy years.

2. Others have suggested a source of warmth: absolutely yes, do this! Cats need warmth more than dogs or people, and if your fur baby is older, she’ll definitely need more assistance with this. In our case, we ordered a couple of those extra large heating pads and kept them on low, covered by a thin blanket, and placed them in her favorite nap spots so she always had a source of gentle warmth.

3. I haven’t seen anyone else mention this: movies or music. Do you have any movies that you watch repeatedly? We found that putting movies (that we rewatch often) on in the background helped her feel like we were around, even when we were out of the house. This worked so well that I use this method for all of my pets! I tend to gravitate towards movies, but any familiar audio could work (music, tv shows, audiobooks, etc.). If she tends to gravitate to a specific spot when she’s yowling, maybe putting the comforting audio in that area can help her feel not so disoriented.

Good luck to you, thank you for being such a loving pet parent, and all our love to you and your fur baby in this difficult and emotional time.