I have not heard any official reason why she withdrew. She probably just simply removed her name off of the lists because she didn't want to play.
She probably didn't want to fly out to Europe for one tournament and then back to Canada the following week for another this late in the season.
I doubt we'll ever get an "official" reason.
Well the funny thing is I thought the exact same thing. Lindsay isn't much for traveling the way she used to be. Still though, I missed seeing her playing the indoor events in the Fall. It's the one time of year she shines better; even on the Summer hardcourts.