Coat "coming in"?

After having Dixie spayed in March, I've noticed that her coat seems to be "coming in", especially her mane and upper chest area.
This was her about 6 months prior to being spayed
http://img.photobucket.com/albums/v2...unnyWindow.jpg
and this is about a week ago
http://img.photobucket.com/albums/v2...moteKeeper.jpg
You can even see a difference in the pic in my sig that was taken in about April and the second picture above.

I know of two things that could be contributing to this growth. One is age, though I can't imagine that much in a short time and the other is that she comes up here on the desk to be combed but it's not a daily thing.
Could getting spayed also contribute to this? Would it be because she's "healthier" now and her coat's in better shape?

I never noticed this before with my other females but she was almost 4 when she was spayed, I didn't have to wait that long to spay the past females I had. I only have two other males now and the same can't be said for them...but again, Toby was 9 months and Churchy was 1 year old when they each got neutered.