The guy I like is sending terribly mixed messages. Help!

If you are more direct, he will also have to be more direct. You could always make a bold move and ask him out, and then you’ll know for sure how he feels about you. Of course, it makes a lot of sense if you are unwilling to do this, but you should still try to give him more opportunities to express how he feels about you. Try to spark conversation with him when you can and see how he behaves during it. Does he seem to enjoy talking to you? Does he seem eager to keep the conversation going, or does he seem perfectly comfortable ending it and doing something else that doesn’t involve you? 

I don’t think the guy that my friend likes is right for her. Should I say something about it, or just watch it play out?

Your course of action should depend on why you don’t think the guy your friend likes is right for her. Do you think that he is a danger to her in some way? For example, do you think something about his tendencies, beliefs, or behavior will injure her feelings? If so, it is important for you to express your concerns to your friend, so she is warned. It would most likely be best to do this in a casual manner, saying something such as, “I don’t know, he seems like he may be more inclined to do x, y and z, so he may not be your best option…”

On the other hand, if you simply think the guy isn’t right for her for a less serious reason, such as because they are in different friend groups, or because they enjoy different pursuits, you don’t have any clear evidence that a potential relationship between them would end poorly, and therefore it would be best to not say anything, but make sure you are there for your friend as she navigates this new relationship.