Where Did This Go Wrong... Was It ME?

I am presently exchanging emails with a former friend about money she owes me for editing work I did for her.  The promise to pay came with the initial request and there have been some exchange of monies.  I relied on the her word that she would pay me and did not have her sign a contract with me from the start.  It is now almost 3 years later and she and I are exchanging emails about said money again.  I hear a tone in her words as she asked me "how much money do I want from me"?
to which I replied "based on what you sent me and what was returned to you, how much do you think it was worth"? This is a mess!  I should have known better but, we all sometimes trust in places that we should not.  The Lord is our ultimate source and as I ponder what went wrong, I can only give account for my part in this and that is that I did not ask God if I should enter into a business relationship with this woman from the start. I saw an opportunity to make some money and continue to hone my craft, but I don't remember praying about it.  A lesson learned is better than one taught.

Thank you Lord for this lesson that will help me as I go forward in other areas of business.  I will pray and wait for an answer before moving forward with an expectations that only I share. There is enough fault to go around.