I offer a clean, respected, well-maintained vehicle with features such as Caraoke, Light shows, etc., FOR $5.

If you offered to pay me $5 to take a ride in a Tesla with “Caraoke, Light shows, etc.”, I’d still pay $10 to take a ride across town in a shitbucket.

Try to negotiate for a bit more and take the money and run.

Suck it up. Leave a non-emotional response if you must, but bad reviews are part of business. Your first instinct should not be to get a bad review removed, even if it’s from a person in cognitive decline. It should be to get more good reviews so that the one bad review isn’t a big deal.

In most cases, you are under no obligation to tell your employer about your employment/business activities that take place outside of your employment (i.e. during your non-work hours and using your own resources).

If you do any work on your business during your normal work hours, use any resources from your job for your business, etc. there is risk that if your employer finds out, they could terminate your employment and take legal action.

I appreciate your business over the years but we are no longer doing handyman jobs.

That’s it. Be honest and don’t feel bad about it because there’s nothing to feel bad about. You’re not obligated to continue providing your labor to anyone, and anyone who suggests you are is entitled.

If you want to be really nice, get a few referrals and offer those to her.