I used to have the same problem. I used a shoulder sleezy, and it just rubbed her in a different spot. But there are 2 different kinds of sleezies. One goes in between their front legs and buckles around their withers, and the other just goes across their chest. (hard to describe) I used the latter one, and it rubbed her. You can put show sheen on their shoulders so the blanket can move easily across the shoulders, I did this, and it helped. You may have to get a different blanket bc like said before, every blanket fits differently. I unfortunetly ended up buying a different blanket!!