I have found that if I have planted my peonies too deep, they don't bloom well. She might try digging them up (in the fall!) and replanting not quite so deep. They don't need to be planted very far into the ground at all. Just barely cover the roots.
Also, peonies love sun. I have some in the shade I have to move myself... I thought they got more sun where I put them than they actually do. Live and learn.
I hope this works for her.... otherwise, not sure why they aren't blooming well.