If this horse was campaigned this could be a sign of stress. Try saddling her off side instead and if she stands, promptly offer a treat. What doesn't work on one side often work on the other. Horses that like to lean on a farrier will often stop when the farrier changes the sequence. If one of you holds her while the other saddles, be sure both of you are on the same side. I'd also do this out in the open and not in the confines of a barn. If she still has to move, stay by her saddle area and follow her if she circles. She'll likely quit after two or three, then saddle her. Don't worry about the pad, just saddle her, walk her then remove it. Then put her away and leave her alone. That's a huge reward for a horse.