My friend told me she doesn't like anyone. But I have noticed that she keeps staring at this one guy, Every time she passes by him, she'll stare at him. And when that guy talks to me, she looks jealous. Does that mean she likes him? ( no rude answers)

It doesn't matter if she does. She told you the answer she wanted to give you. If you are truly her friend you would respect that.

Judging from your info, she does seem to like him. I think she must be jealous because he's talking to you, but ignoring? Her if he is or doesn't seem to notice her. I think it's best not to interfere with it. If you want, you can play behind the scenes and help her interact with him if it's not a love triangle between you three. She might not like him and might just have an interest (not love interest) in him.

"Susie, whenever Nathan comes over to talk to me, I have a feeling that in spite of what you told me before, it looks like you really like him. I want to help you feel more relaxed when you talk to him so you don't feel nervous. I like to ask him about _____ because that's one of his hobbies. It's a great ice breaker as it shows you're listening to him. You should give that a try the next time he comes over."

Girl Here: Many kids get nervous when they have to actually talk to someone as most of their "talking" happens in text. So she could have told you "no" she doesn't like anyone only because if she said "yes", you would see how nervous she gets.

If you don't like this guy yourself, then I really cannot see the matter with how your friend is acting.

Why does it concern you as to how you think she's looking at anyone?  If she likes this guy then there's nothing wrong with that, and if she doesn't like this guy then there's nothing wrong with that.  If she likes him but hasn't told you, then that means she doesn't want to make a big deal out of it, or certainly doesn't want you to know for whatever reason that may be.  Leave her be, if she wanted to tell you she would, however she hasn't and so you have to take her at her word when she says she doesn't like him.