If there isn't any physical contact, is it still considered cheating?

How many times have people asked whether they were cheating or not? It’s a very confusing thing to determine because everyone has different views on the subject.
Okay, here’s the problem. My friend has a steady, serious boyfriend. She loves him and he’s very “hot” (I’ve seen him without a shirt on :) ). She really likes him, but there are moments when he’s a BIG jerk. There have been times when she was deep in her tears, wondering whether he was worth her time. That’s when she tells me every bad thing about him (I’m sure everyone has had this kind of conversation with their friends). She tells me that they don’t really have anything in common. She says he does nothing but play around with “stupid” cars, he hates everything but sports, he says the most ignorant things sometimes, and does many other selfish things that would be considered inappropriate to mention in this PG blog.
Then she tells me about her feeling for a friend of ours. She tells me that she loves her boyfriend, but she’d much rather spend her time with our friend. They have so much in common that she values their time together more than her time with her boyfriend. I asked her if she had strong feeling for our friend, and she said that she did and that there have been times when she wanted to kiss him. But she didn’t of course, she’s not that type.
“But would you consider this cheating?” she asked me. “I don‘t want to break up with my boyfriend, but I'm afraid I'm doing something bad that'll make me lose him,” she told me.
“I seriously do not know,” I told her. I really don’t. I always thought cheating involved sex, but maybe cheating involves emotions and sex usually just comes into the equation. But what about times when people have meaningless sex, one-night stands? It’s still considered cheating. So, maybe emotions don’t have to come in the equation. IT’S VERY CONFUSING.
Then she asks me, “What should I do about this?” She wants to know if she should tell her boyfriend. But you see, he’s the controlling, “quit looking at my girlfriend” kind of guy. She’s afraid if she mentions this thing she considers nothing, that he’ll see it as her cheating on him and break it off.
I have no idea what to tell her. I’m usually the one my friends turn to when they’re at a crisis, and I feel bad that I can’t really help her. I hope someone could shed some light on this subject for me.