Your friend is morally correct and most of the answers here also take the moral high ground. And perhaps morally, if you had the money, you would pay up immediately.
However, you don't have the money. Perhaps you could get a loan, but that could be very expensive and problematic for you, so the best person to get the "loan" from is perhaps the injured party, by paying her in installments. Legally, the situation is exactly as Peter Pedant describes above, so follow his advice.