I'm getting a vibe that there was a "leader buddy - follower buddy" thing going on here.
That's a possibility as well. There are also people that aren't comfortable being away from the line and prefer keeping it in sight at all times and following it rather than just diving close enough to reference it if needed.
I find it hard to imagine that I'd panic and bolt if I had the line, any line in sight, but there's no way to know what what triggered her response. Once someone crosses that threshold all of our rationalizations here go out the window because they're no longer acting rationally.