installation failed

Trying to update my mom's 2020 MacBook Air from Big Sur to Ventura and it keeps failing. "Installation Failed. An error occurred while installing the updates." It has plenty of disk space (188 GB). What I've tried so far: Reboot the MBA. Boot into Safe Mode. Reset PRAM/NVRAM. Downloaded...

I'm hoping some of you gurus can give me a bit of direction here - I am not completely useless with Macs, but I am far from an expert so please forgive me if I am missing anything obvious. I have had this nasty problem when my 2011 MBP 15 starts up where I get 'thin red horizontal lines' on the...