We all get comfort from different things, I don't think it's too weird for someone to want to swing, that's what they were made for afterall. I like to drive with the windows down even when it's cold out and listen to electronic music full blast while smoking cigarettes. That might be weird to some people, but it's sexy to me.
Seriously though, maybe just ask her, gently. "Sissy, why do you like swinging so much?" I don't have any brothers or sisters though, so I dunno..
__________________
|