For many of these women with very long hair, what we see as major cuts they can see as routine. They don't cut their hair often, either by choice or out of laziness, and when they do, they take off a lot. I had a friend in school with gorgeous blonde hair that varied from just past BSL to hip length when I knew her. She considered getting 6-8 inches cut off a "trim." When we first started hanging out and her hair was just past her breasts, she very casually mentioned that in the previous 6 months she had cut something like 14-16 inches. She once cut 6 inches, taking it above her waist, and she claimed I was the only one to notice.

A lot of women also seem to have a length at which their hair starts to annoy them. For her, when her hair got past her belt and/or started piling up in her lap when she sat down, she started complaining about it being too long. The unfortunate cases are where they get annoyed when it gets a few inches past their shoulders.

If the girl is in her 20s and single, and she "only" cut to just beyond BSL, there is a very good chance it was a maintenance cut and not a long-term change in style. If she cut it to her shoulders or to her chin or if she cuts in shorter in the next few months, that might be a one-way trip.