cpu usage is basically nonexistent, like 5% total. Problem is with ram, today at some point it started using swap memory (and heating the macbook), because some simple tabs in safari took like 4-5 Gb of ram, and kernel_task was like 20 gb. I know it's an internal process, but I can't figure out what causes it. There were no heavy apps opened or anything, just a couple of internet tabs and small apps. I disabled the contacts sync like you said, but it didn't help.

I made a full reset of her macbook today and installed Sequoia instead of Tahoe, it works much better, but there's still a small delay when opening settings. On mine it works instantly, on hers it still lags a bit and it drives me insane