+1 on filing a complaint.
Having gone through a buy/sell last year my advice would have been to question EVERYTHING, multiple times if necessary. (Drove my agent nuts, but it worked out.) And trust your gut. So a couple of after the fact points. Hopefully, this doesn't sound like a lecture.
1. Agents are expensive but the great ones are worth it. The most popular agents aren't necessarily the best agents. They are just better marketers. But ever wonder why they have to market themselves so much?
2. I would have conducted an interview with her without your wife present. No interview. No deal. She passes muster, then have a joint meeting. This is a 6 figure transaction. Your money, not the agents. Make sure they are worthy of that trust.
3. HOW did she know the buyers didn't have the money? I would have asked her to prove it before walking away from that offer. Also, what kind of earnest money did they put up? Ask for more! There are plenty of points to negotiate in a R/E transaction.
4. Even if she had a plausible explanation, it's EASY to research online to learn some details on the buyers to help you make an informed decision.
5. The people who don't look like they have $ are richer than an entire block full of the $30k millionaires she associates with. Hell, she's probably one of them.