The thing is that her buddy left about 6 months ago and this just started 2-3 weeks ago. She is fully retired and no longer ridden and she has access to pasture all day and a paddock 24/7. Could it be a delayed response?
It could be that she has done it without people around and we haven't noticed it until lately. Would Cushings cause an increase in appetite? Maybe she is begging for more hay? I don't know though because she is pretty obsessive about it.