I agree with everyone who's said not to tell her it's stupid- there just isn't any point. The likelihood is that she knows it's stupid but by saying it to her, you're passing judgement and she's not going to want to talk full stop. At times it'll be so frustrating for you- feeling like you just can't make a difference. By being there for her you are making a difference though, even if you don't directly talk about the situation. It sucks but being there is all you can do unless she says otherwise.