Disappearing is a trade, and it is a bad one. You get out of a few uncomfortable minutes, and in return someone who treated you well is left holding the idea that they did something wrong. They never get the correction. You get to know for a long time that the easy exit was there and you took it.

Send the short version instead: this is not working for me, and thank you for being good to me. Do not rehearse it into something clever. Two awkward minutes now is lighter than carrying the other thing around.