Your thoughts on just a saddle blanket? (western)

Not enough cushion for the back. There's no shock absorption in a wool (or synthetic) blanket. And the blanket in the above photo is sideways....

As others have said, you need at least 3/8" of felt (preferably natural fiber) to prevent the development of back soreness. Actual thickness required will vary with saddle fit and horse conformation/fitness.

It's not sideways. I have it folded. It is meant to be like that.

I agree with others, I would get a thin pad and maybe put a saddle blanket over it. Western saddles don't have that much cushion, where as english saddles do and fit closer to the horse so you can get away with thinner pads. Maybe find a thin gel type pad that would absorb impact and provide more cushion?

You have it turned the wrong way. Both tassels should be at the back. Also, if your horse doesn't want any thicker pad, then your saddle may be too narrow for her or you have it too far forward. The front edge of the front conchos should be 2" behind the back edge of her shoulder blades.

The folded end should be at the front of the horse, both tassels at the back of the horse. You have it sideways. Either that, or it's not a real horse blanket and the pattern is non-traditional. Horse blankets almost always have the stripes going across the short side.

Like this blanket, which is a 30x60, meant to be folded over.