How to collect on a loan based on an oral agreement and no witnesses?

My aunt lent $3000 to a friend/co-worker in 2013. She told her friend that he could take his time repaying (the loan was to help with funeral arrangements and said friend was in mourning). She now wants to recover the money, but they only had a verbal agreement AND she (very unwisely!) paid in cash. She did tell me that her friend has told other co-workers that he knows he needs to repay, that he feels bad, etc. When my aunt approached him regarding repayment, she says he becomes upset and defensive. My aunt feels uncomfortable asking their co-workers/mutual friends to be witnesses, but I feel they are her only hope as there is no other proof. She is considering small claims court, but how will she know that her friend won't claim that it was just a gift??