A holiday by myself sounds like a friggin dream come true. Like if I got the green light to go somewhere hot and sunny for a few days alone, I would be all over it. In fact, my husband is going on a mountain biking trip next summer with some friends and I'm already thinking how to best use the alone time that I earn from him going on that trip.
If she offered it up and it's your 50th birthday I would definitely go. Maybe "the trap" is that she's also going to want to do a solo trip herself sometime soon or for her 50th or something.