The only thing I can suggest is that you talk to her. Ask her what you can do to help, tell her you are there for her. She has been your protector for so long, but it goes both ways and maybe she will let you know of something you can do to help her.

If you don't have good communication with her maybe you could simply talk in her general direction. Tell her you know she's upset and you don't know what the problem is, but you are there for her if she wants to talk to you, and you are willing to listen and do whatever you can to ease her pain.

But only say it if you mean it.

That's what has worked for us in the past anyway.