Wow, Glen, What a drag.

You said she is getting on., and has a clean bill of health. Has she been given the expensive but very useful "senior blood panel"? This would reveal things like kidney disease which is common in older cats. Has she has a dental exam recently? it may be that kibble is no longer an option for her. She may need to go on a special senior diet. I don't know how thorough your vet is, but there are a few common issues with older cats.

The bizarre howling and peeing and now the barfing to me indicate some sort of health issue.

I recommend you tag Beth Bach at the end of this piece. Beth is former cat rescuer and has a very long list of solutions to problems.