Arthur Deikman wrote an excellent book on this which I highly recommend if you haven't read.

The Wrong Way Home: Uncovering the Patterns of Cult Behavior in American Society

(Reviews from Amazon)

From Publishers Weekly
Members of political or spiritual cults exhibit conformity, a yen for dependence and susceptibility to authoritarian leaders. The same behavior, Deikman argues, can be observed in ordinary people--in relationships, the workplace and family life. For example, in the "corporate culture," this California psychiatrist has found threats of censure and expulsion, and an inhibition of active strategies and dissent--all favorite cult tactics. Other examples of cultish shenanigans cited include politicians' cultivation of a benign, powerful parent persona; military leaders who "imagine enemies where there are none"; the complicity of a subservient news media in supporting the status quo; and the humble compliance to God's will urged by religions. Although Deikman sometimes stretches the analogy of cult behavior too far, his provocative book uncovers a psychopathology of everyday life in a discerning analysis.
Copyright 1990 Reed Business Information, Inc. --This text refers to an out of print or unavailable edition of this title.

From Library Journal
The author, a psychiatrist, argues that cult behavior is not limited to members of religious groups but is based on childhood desires for meaning and dependency that we all share. He describes normal society as "an association of informal cults to which everyone belongs," including our educational, business, and other cultural structures. Although we live in a democracy, cult behavior manifests itself in our unwillingness to question the judgment of our leaders, our tendency to devalue outsiders and to avoid dissent. We can overcome cult behavior, he says, by recognizing that we have dependency needs that are inappropriate for mature people, by increasing anti-authoritarian education, and by encouraging personal autonomy and the free exchange of ideas. This is a provocative book that should have appeal for a wide variety of readers. Recommended for most libraries.
- Lucy Patrick, Florida State Univ. Lib., Tallahassee
Copyright 1990 Reed Business Information, Inc. --This text refers to an out of print or unavailable edition of this title.

Thanks everyone for your replies. Sorry it's taken me so long to respond!

I've long since given up on trying to make the friendship work. To be honest, I think I gave up on the friendship long before it ever ended, somewhere around the time when it was clear to me what Landmark was, and how she was involved, and what that meant in a deeper sense.

But I was thinking again today about her response, and about the question I asked, and I didn't see much (if any) correlation between the two. She never came close to answering my real question. My exact question was, "How much of your decision (to terminate the friendship) was influenced by Landmark?" I was careful not to point fingers or place blame, because I knew the reaction that would get. I was thinking she would have "gotten" something during a weekend retreat that helped her come to the decision that maybe she would have shared with me.

While it may sound conceited and a bit self-absorbed (please excuse me in advance), I believe that part of the reason the friendship failed is that she was seeing me accomplish things (without the help of Landmark, of course) that she herself was failing at. These are things that she's been looking to have "breakthroughs" in from her participation. For instance, it's the first time in the year and a half that we've been close when I'vebeen in a healthy relationship and she hasn't. One of her old selling points in trying to get me to enroll was that Landmark would help me make a "breakthrough" with my relationships with men. I also got a raise and a promotion at work, and I didn't ask for either. And I didn't do Landmark! A part of me believes that it's hard for someone like her--who believes so strongly that Landmark can only do good, and conversely, good can only ever come out of Landmark (and nowhere else)--to see good things happen to me while I profess my disdain for all things LEC.
Does any of that make sense? Or do I just come off looking like a completely self-important b*tch?

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leftcoast8
A part of me believes that it's hard for someone like her--who believes so strongly that Landmark can only do good, and conversely, good can only ever come out of Landmark (and nowhere else)--to see good things happen to me while I profess my disdain for all things LEC.
Does any of that make sense? Or do I just come off looking like a completely self-important b*tch?

That makes perfect sense. She wants to enroll you, but can't find that all important chink to use against you. She's probably also frustrated that you're doing the opposite of what she's telling you you need to do, but still things are working out for you. Despite what LEC tells you, they really are desperate to be right (even when they're claiming that being right doesn't matter, really it does, because Landmark still has to be right).

I understand your disinclination to remain friends with her -- but perhaps you should remember that there was something in there that you valued before she got sucked in by Landmark. I appreciate there's not much you can do now, but she may need your help if she ever snaps out of it. I'd be tempted to e-mail her back and tell her that you don't mind her not talking to you, you were just curious as to the causes -- and that if she ever gets out of Landmark and needs your help, you'll be there for her. (me being me, I'd probably belabour the point and say that you don't want her to contact you when she "stops making you wrong", because you don't want to be harrassed into trying Landmark -- but I always fall on the wrong side of subtlety ;) )