Could I get your advice?

I have this friend. And this friend is a worry wart. And whenever she gets a tiny idea in her head it burrows in and starts to pick at my consciousness. I mean HER consciousness! Anyway, my friend has gotten this idea that a certain someone in her life is unhappy. Not only is she afraid that this person is unhappy, but she's afraid that this person will leave her. She's afraid of all this because she doesn't show any emotion when she talks about her skin disease. (What a coincidence!) But the reasons that she doesn't show any emotion anymore are so crazy confusing to a normal person that even I don't understand them. She really REALLY hopes that she's just worrying herself over nothing, which she does all the time so it's no big deal. And her and this certain person are supposed to talk about it tomorrow. What should I tell my friend that she should do?