That depends on which of these rephrasings would capture what you're saying.
"Since when does moving from non-threatened to threatened provoke?" It doesn't, but to get into the main area of the temple you need to move through Alexia's square, going diagonally from E7 (threatened and which the creature already empirically proved it can attack into) to D6 (also threatened).
"Since when does moving from a threatened square to another threatened square provoke?" Since 3.5ed came out; I hear that 5ed looks at whether you're leaving the threatened area entirely, but 3.5ed only cares that you're leaving one threatened square.