using someone elses card with consent

I live in the uk. I helped my friend out by paying her mortgage for nearly a year as she was having some financial problems. She gave me one of her credit cards to take back some of the cash she was owed me (about 70% of what she was due me) Since then we have fallen out and she is now trying to take me to court to get me to pay the credit card bill, how do I stand legally on this matter. She has her family lawyer sending me letters with court threats where really she is still due me money.

Help..does anyone know the scottish law on these matters.

[able1]

If you can show she authorized you, you will have no problem. But you need to gather up any and all evidence. Emails, letters, witnesses, phone records--anything to show she did authorize this.

In the future avoid any such use for exactly this reason.