Buyer saying car has dodgy mot

Hi, I’ve just joined here as I would like some help or someone to put my mind at ease.
I bought a cheap car from eBay with no mot, my husband is a mechanic and mot tester, the car needed a clean up, new tyre, front fog light and a few other little bits, husband took it for mot and failed it on another tyre as noticed it was lower than first thought and bought a new tyre and passed it next time with advisory on another tyre and something else but can’t remember what it was. Anyway sold the car for small profit and a week later had the lady at garage my husband works at saying car wasn’t running right and it’s rubbish, garage couldn’t look at it straight away so sent her to next garage, the car needed a new lambda sensor and crank sensor (car had been off road for a year before I got it) she then started texting me saying car shouldn’t have passed mot? And was threatening me, then said the engine light was crossed out, the engine light came on and off when we had it. Forgot to add that she had been driving around with oil light on, which my husband said she shouldn’t have kept driving it. Anyway she was quiet and it’s been 5 weeks since I last heard from her and now she thinks we own the garage she’s come back threatening to go to police and trading standards!! It’s making me feel ill, as far as we know we have done nothing wrong??? Worried as husband tested it and I sold it. This was a £550 car. Please help