Misty's approach is just the way things ought to be handled, IMHO. Sometimes Ladies book "iffy" appointments without being open about it. When they know there is a chance they may have to cancel (travel issues, "real life" intruding, possible visit from "Aunt Flow," etc.), it really helps to let the guys know ahead of time, as Misty did.
If I got a message like that, and it was someone I was planning to see locally, I'd say: "No problem." If it didn't work out, no biggie - I can see anyone here in MN almost any time. But if I was travelling, and had limited time, a hotel room to book, etc., I might say: "Maybe next time," and go for someone more certain.
The point is, when the Lady is up-front about it, the Gent can act accordingly. Much better not to book if a cancellation would be a real disappointment, and see the Lady some other time. If a cancellation would be no big deal, the Gent can go ahead and book a date, and keep his fingers crossed.
And BTW, I think men (I wouldn't even think of calling them "Gents") who double-book are real low-life. Things can come up in our lives that force us to cancel, but double-booking is basically PLANNING in advance to cancel on one of the two Ladies, and thereby cause her frustration and loss of income. Same applies to Ladies who double-book, of course - professionalism in booking and honoring appointments cuts both way.