You need an english saddle pad, if you get a thin one then you need a half pad as well. Also do you have a pic of her standing completely to the side, the saddle looks a little to far forward but I am having a hard time telling from that pic. As for boots for her, that really depends on what you need them for. For basic ground work (you riding) you shouldnt need boots. For lunging I would use polos front and back, and if she has front shoes then you might want to use bell boots.

When was the last time this horse was ridden. and also when was the last time you rode. I can help you out more once I know that stuff.