If a company is struck off, then the loan will need to be written off. In which case, she will have received a dividend or capital payment from the company and she will need to pay tax on that. HMRC will be looking to her to pay the tax if the company is struck off, she won't just waltz off into the sunset.
Also, when you strike off a company, you accept the liabilities of the company personally. This is because you haven't gone through a formal liquidation process where potential creditors would have been identified and dealt with. So any liabilities of a struck off company would become the liability of the directors.
So in summary, there's no way round it, you've got to stump up to HMRC. Of course if you were a just a bog standard criminal you could just not declare anything to HMRC, and then wait to see if they send you to prison.