Easy for you to say, assuming your PC is clean. I don't think negligent is the right word though. Ignorant maybe? Or some form of naivety? The negligence might be on software or hardware vendors, but grandma isn't to blame for the problem.
Software providers generally lack a duty to their clients to create and sell secure software. Further, generally, when you get hacked, there is only an interrupted causal chain between the software and your loss. Interrupting that chain is the intervening superseding cause of a criminal third-party. Finally, no states allow punitive damages, absent gross negligence in a software context.
when you read or are told not to click on that link in the e-mail, or open the attachment, you should fire up your monitor while you are clicking on the links.
it might be interesting to have an eye on this while you are talking to the phone scammer.