I pay for one lesson a week but I also get several free ride days, because I work there on Saturdays. She gets very little turn out time as far as I know and she isn't ridden much, which is why I think lunging would help a little. I know it would make her more fit, but if I were to lunge her it wouldn't be to 'get rid of the crazy' or tire her out, it would be to give her some much-needed exercise so that she does not have to release all of her energy the moment someone gets on her back. But regardless, I have no control over that, so my opinion on the matter won't make much of a difference. :/
Eolith -- Yes, that may be partially it, and in that case it's a matter of time and patience (and you're right, not lunging). But at the same time she doesn't get a lot of exercise so I have a feeling it might be a mix of both.
Thanks for the replies, everyone! Keep 'em coming