Now she complains the laptop is "freezing up". Rather than wait, she powers it down. I'm afraid of file system damage.
I'm in the same business. It's impossible to know if it's her, software or hardware, until you reproduce the problem. Ask her if she can reproduce it easily on demand and then take it and do it, or do it while she's present. Then you can hit C-A-D/whatever and tell if it's hw or sw.
There's a lot of crap hardware out there (75% of it at least), especially on a refurb. It's very very very (very very very) hard to sell hardware these days if you provide any sort of warranty or reliability standard. You have to vet the brands you sell very carefully and ditch brands the instant they give you trouble. Make up a clear warranty policy in writing saying what sort of things you cover for free.
With laptops, the problem can often be overheating due to dead fan (listen for it) or poor TDP design, or bad ram (run memtest) or slow degradation of the mobo due to static zaps, etc.
Good luck.