It is one of the same its cool catch phrases from the film.
Extremely cool! And I love the reactions from the female divorcee support group.

I've thought the same, but watching this show on video and cable tv over the years, we hear it. In the theater, you've got one shot to hear it. It was the best line, the most important line in the movie and she repeats it because of that, I'm sure. For emphasis, and so all can hear it.

Ah, but to me the "bringing it up a notch" is where the problem is. If there were such a danger of the line not fully sinking in and, really, couldn't that be true of ANY given line in a movie? then she could have said it
as if she herself didn't realize what she meant until the moment she said it
, which is apparently what Crowe & co. were trying to convey. Like this: "You had me at hello.
[very brief pause]
You
have
me."
What they DID do, repeating the line in full, makes her sound more
conscious
of the wording than of the emotion itself as if she's aware of what a cool line it is and wants to play it for all it's worth and thus it doesn't seem spontaneous enough. "Bringing it up a notch" to make sure we get it? That's what
makes
it sound un-natural.
(Unless they were
trying
to suggest that her character had the line planned in advance. I doubt it, though.)
Anyway, this is just my opinion, but I stand by it. Maybe I'll go get some software and do my own edit
not
.

I liked the repeat. She says nothing for so long during his speech and then finally says this, it's like wait, what did she say? We hear it, but maybe it doesn't fully sink in. Repeating it brings it up a notch, and we catch its full effect.

I just wish I had the ability to do a small edit in that scene. When she says "You had me at hello" the first time: Great. The sentiment sounds spontaneous. We GET it, right away. But then she goes and
repeats
the line, and it begins to sound planned, rehearsed, like her character is saying it more
for effect
than as an honest expression of feeling. One time was plenty. Don't oversell it.

No. This line was invented by writer-director Cameron Crowe. It is one of the same its cool catch phrases from the film.