Is okay to ride a healthy horse with a backbone that sticks out?

Is this horse an older horse? Some older horses tend to get a little sway backed and the backbone with jut out. As long as u are padding up her back with pads good under the saddle and she doesn't seem to have any problems when u get on her back u should be fine. If it was hurting u she would let u know, some horses groan when u set on them, some will not break into a trot or gallop, some will actually buck to get the pressure off, some will stop and turn their head back to their back, and after u ride watch to see if she is very stiff acting when walking. I think you're safe in riding her if no signs are demonstrated to u.