First of all, even the high end ladies get tons of cancellations. Many times people don't show without even canceling. It just doesn't sit well with them. Of course they've heard every excuse in the book. And this is a hobby that just doesn't engender trust and honesty. Nevertheless, you have to be honest, and cancel. Especially if it's with someone you've seen many times, she has to believe you. If she doesn't, she runs the risk of losing a long term client. She won't put you on any black list. However, if it's a new lady, you run the risk of losing her because you haven't built up any trust. I don't think she'll put you on any black list because you took the time to communicate, but she might take you off her own personal list. That's luck of the draw. But let's say you don't cancel, you get her sick, and somehow she's able to pin it on you. She just lost about ten days work, or several thousand dollars. She's not going to be happy with you. That could get you blackballed.
But what if the situation is reversed? She's sick, and she doesn't cancel? It just happened to me. Two Saturdays ago I didn't notice her symptoms until about halfway through the session. Sure enough, 72 hours later, I was sick. I know it's Christmas, the worst possible time for someone without sick leave to be out of work, but she absolutely should have cancelled. She did not! Now I was sick, and I had to cancel the two sessions I had set up for last weekend. What about those two ladies? It's Christmas for them too. That's why you have to cancel. It just hurts everyone on down the line if you don't. If someone gets mad for canceling, then I think it's time to move on anyway. Oh, and the lady who got me sick was a lady I've seen regularly for the last few months. So yeah, she got the Christmas session, but now she's on my blacklist, and it's going to cost her thousands down the line. If you're sick, just cancel!!