Basically, it implies that she fell waaaay before that conversation. I seem to recall that the Handmaiden mentions going on missions to obtain holocrons. And we know
that Atris has tons of Sith holocrons. I imagine that it would take time to amass such a collection. My guess would be that the exile's decision to go to war was the beginning of her fall. By the time we encounter her on Telos, she was pretty manipulative--e.g. leaking the exile's information so that she could use the exile to draw out the Sith.
Anyhoo, just my