I promised my sister that I would go sky diving with her when she was old enough to, but I didn't think she's remember. I'm horribly afraid of heights.
How long ago was it?
I promised her about 8 years ago.  I was much younger also but now I have two kids and don't really want to do it.  Thinking about dying or even just jumping off a ladder, much less a plane, seems awful!
Maybe you can talk to her about it?