I'm going to cancel at the last minute
Why would you cancel at the last minute?
I was going to have sex with the woman, which would have given me little to no respect for her.
It is good to build intrigue but it is not good cancel at the last minute. She will just think you are flaky.
It's fine, she is a slut anyways.
Wow, you really shouldn't call woman that, no matter how much sex they have. If you don't want to loose respect for her, just don't have sex with her or cancel now before it becomes the last minute.