I think it was a combination of things... But once we find a good hair growing regimen are we really to never try anything new again? I don't think that's a good takeaway from this at all. She didn't do anything crazy. All she did was try a new hairstyle that required a few new products. It's unrealistic to expect that one will never do those two things again, because they now know how to grow their hair.
I do think that the lack of thorough detangling attributed to the set back. It may work for the way she normally wears her hair. But it did not work with this style and/or set of products. The regimens we put together-- the tools, the products, the methods-- they go hand in hand, and you can't always sub out one aspect for something entirely new and expect to get the same results as usual.