Is This Delusional Love Disorder?

I've had a FB friend (online only - never met in person) for 1 1/2 years. (We met in a FB group for a mutual hobby.) She and I became very close, and she shared all her deepest secrets with me. (She is in her mid 40's, and is currently undergoing a divorce.) One of the things she told me, is that she has been communicating with an old platonic high school friend for 7 years. During this time, both have been married. They have never seen each other physically over those years. She set up a secret chat room for the two of them, so that they can send each other messages and "racy" pics. She obsessively tracks his activity on FB and other places online, as well as follows his two daughters' online accounts (that she discovered) for clues as to what is going on in his life. She is certain they are destined to be together someday, even though he has told her things like, "I'm happy in my life. I am not leaving my family. I don't own you. You are not my girlfriend." But nothing deters her. She has sent me very long messages she has written to him, declaring her love for him, promoting herself and what she has to offer him, etc....and asking my opinion of them. In the beginning, when she first told me about their relationship, it seemed that he really did care about her...but I slowly began to realize, he just wants her as a diversion, a chat buddy, and does not really have any true romantic interest in her. She thinks that the only reason he isn't responding to her romantic attempts, is that he has a minor child at home. (And that in four years when that child is an adult, he will come to his senses.) I listened to hours upon hours of this "soap opera" because her friendship was important to me. (Yes, this is a separate issue that I have - I became addicted to her friendship, since we chatted nearly every day for months and months.) Anyhow, he apparently has lost interest and hardly talks with her anymore, and she is in a deep depression...and has stopped communicating with me, too. I have also suspected she is manic depressive, based on her sudden mood swings while I was chatting with her. (I have also spoken with her on the phone a handful of times.) I almost got her to see a counselor (not specifically about this...but about her many other issues), but she can't quite bring herself to do that. I'm feeling guilty now, because I did sort of encourage her communications with this guy (because I wanted her to be my close friend). She is now even suicidal over this guy's latest declarations of uninterest. And she isn't really talking to me, currently. (She has done this before - not spoken to me for weeks at a time while she "works through" something.) Is there anything I should/could do for her?

I don't know about your ONLINE friend. But please come out to REALITY. Have a social physical/real friend outside the computer.
What I don't understand is - "why the hell do you want to be a friend of such a person" ?
Please retrospect about your mental situation also. As normal people have good amount of friends and are not lonely. You seem to be a very lonely person. Go out and spent time with Family & Friends man !!