I think that at the moment you should focus on you and see what you could change to become a better Clay. From what you told us it seems that she has few issues but at the end of the day she is 43, and if she thinks she is depressed only her can make the first step. It has to come from her, as if someone pushes it on her she'll blame that person, and there will be no result because she'd have gone again her will.
Think about what you'd like to become and be strong for your kids. Unfortunately we can't chose our in-laws :-)
