Re: subtle comments?

It sounds like it's time for a heart-to-heart honest conversation. Don't do it in bed. In fact, sometimes it's better to talk in a neutral space - a park, a restaurant, the car on a drive,etc. Do it when you are both calm and ask her. It may be that the relationship has run its course or it may be that she's just frustrated with other things. You won't know until you ask her.

Good luck!