I only put it on here to tell my friends on horse forum about not to be told that I have problems and that I handle her wrong on a daily basis.
I'm sorry, when you said "she's just not working out" I assumed that she was semi-new, as I generally hear that expression about new things.
I would say that the fact that she isn't working out is a "problem", or moodiness is a "problem", not implying that you yourself have problems, but that over all there is a problem, as otherwise you would not think about selling her, I just thought that it would be best to evaluate your situation rather than perpetuate it, if you hadn't already. I was merely offering you things to consider.
Out of a potential buyer I would be looking for someone who is the best fit, don't try and sugarcoat things for a sale (many people do) if you after the best home for you horse. If you are very particular about matching her up well offer a short trial period.
As for looking for another horse, all the questions in world cannot give you as much information as hands on experience. Try the potential horse over show jumps, and if possible ride it a few times, one of the times try and catch it, tack it up etc all on your own. If possible see it at a show, or out of its comfort zone.
Best of luck.