[Anonymous]

She is a senior, some dogs and people get skinny as they grow old, just look around.

Anyway, I would broil up a little chicken liver, chop it up and mix a spoonful of it with her kibble. For a couple of bucks, it should last 4-5 days (cooked) in the fridge.
Consider adding other cooked chopped up lean meats to her kibble, chicken breast, steak…no bones.