I'm really sorry to hear this happened to you. I just don't understand how this other lady contacted you to warn you. How did she know you needed to be warned?
I'm curious as to why you gave her your mother's ring, did you live in the same city?
Being an empath doesn't make you a good person. It means people feel the energy of others, it doesn't mean it affects them in any way or makes them more caring or compassionate. For many it does, but there are just as many it doesn't. This is also how they may know who they can take advantage of easier. Experienced empaths can turn off their ability to feel people's energy.
Did you have this loan agreement in writing? even through text or email? If so, it may be considered a contract, but also serve as evidence to take her to court and to file a police report. I'm just wondering why you haven't filed one yet.
I hope that you will take this further and try to get your money back with interest.