Does he have the means to pay realistically?
I realise he is working but is he earning enough?
How much is the loan?
She needs to get to the bottom of the sum in question. That will be critical.
In principle though, she could sue him at the civil courts. Clearly there was a contract that she would guarantee this loan and that is fine but a court will usually accept that the debtor is the primarily liable person.
If he is working then he would be worth suing.
The issue really is the amount owed and, in particular, whether with costs and interest it would be over £10k. £10k is the limit for a small claims court sum. To sue cheaply she needs to do it at the small claims court.
Might be worth getting a solicitor or a barrister under public access to send him a letter before action though before issuing.
Can I clarify anything for you?
I'm not sure what you mean?
So they don't have a CCJ against her ?
Well, she could refuse to pay but then they would seek a CCJ which is not desirable.
She could sue for the sum that she has actually paid or she could take over responsibility for the loan and then sue for the full amount.
All the best.