Prospective tenant has CCJ

Other

Reference checks on 2 prospective tenants one was ok but the other tenant (who has a verified salary of £120,000 pa) has come back saying that she has a CCJ for £1000 which she claims she was not aware of. She has checked it out and she says that she made a claim for PPI and the Bank told her that because the PPI payments would more than cover the amount owing on the card that she did not have to make any further payments. She also claims that all her coraspondence relating to this card had gone to another address that she moved from some time ago
What is the best way to deal with this and would her story be credible your advice would be very much appreciated.
many thanks