K.D.
You may believe in the honor system but not every one does, especially people on Craigslist. Since there is no binding agreement, other than word of mouth, there's not much you can do. Sending her a self addressed envelope is like giving her a free stamp. I highly doubt she will send you the money if she hasn't given it to you already. Personally, I would chalk it up to learning a lesson and move on. It's not worth the stress and aggravation. Next time, get the cash first, and then give the buyer the items. I don't trust anyone and that's how I operate because fool me once, shame on you, fool me twice, shame on me. I'm sorry this happened but craigslist is a hit or miss. I would just let it go...