Taking the piss (out of a mattress)

[Spinxsta]

Our cat is trying my patience! She went through a phase around Christmas - Easter of peeing over DD's bed. We've taken her to the vet and she's on antidepressants but it turns out she's just a dickhead! We bought DD a new mattress after her old one had maxed out on baking soda and detergent. The kids are now conditioned to close their bedroom doors even if they're just popping to the toilet.
Anyway, DS must've left his bedroom door open and we didn't notice but his bed was dry and stunk of cat piss. So, I sprayed is with a vinegar solution and now it stinks of vinegar and cat piss. He's not happy about the smells.
So, 2 questions:

1. is there anything I can do to salvage the pissing vinegar mattress?
2. what the hell do we do to stop her pissing on beds?

She's 8-9 years old and has never done this before. We have tried: moving her litter tray, changing the type of litter, giving treats on the kids' beds, feliway, spot on calming stuff, calming pills, painkillers... she's been checked out by the vet and is "a picture of health".

What’s her litter like? Is it a rough one or a fine f
granule type?

She's always had the gritty stuff but we changed her to the granules when she was destroying DD's bed.

Is she neutered?
How many litter trays does she have access to?
Is she showing any other signs of stress such as over-grooming?

You need to use a proper pet enzyme spray on pet urine - vinegar etc. won't make any difference as it won't break down the smell. Simple Solution is a great product but ideally it needs to be used as soon as possible and on fresh urine as once it soaks down through the mattress it's almost impossible to get rid of.

You could try a waterproof mattress topper on all the beds so you "just" need to change the sheets as opposed to worrying about the mattress but that's more management than anything else.