as mare and I were walking, I noticed she was walking sideways.. what does this mean...

mounted or unmounted ?

unmounted.

Hmmm, could have spooked at something and wanted to walk around it- possibly mud puddle, something in her path, or she noticed something in the distance or behind her that got her attention and was trying to turn while walking to see what it was.

Doesn't sound like a pain issue. Was the area she was at, a new place to her? Also was she continuously walking sideways, or just for a short distance?

If she is trained to sidepass and you were mounted you could've inadvertantly cued her to sidepass?

Hehe, good question also.

shes been at the ranch her whole life.. and I don't think she was spooked. she keeps walking sideways everywhere we go. btw ty for helping:P

My next thought would be haha... maybe it could be a pain issue. She could have something hurting her, or something out of line. Maybe ask a Chiropractor and see if they have ever heard of something like this?
Very odd. Just wherever you lead her? Walks continually sideways behind you? How about when she is in the pasture, or stalled? Does she move sideways at all?
Unless this mare just enjoys her sidestepping techniques all over the farm, possibly you're equipment is crooked? Maybe check halter/lead (whatever you're leading her with), try something different to put on her.