Though you mentioned before that Mathilde thinks Naggaroth might be connected to L'Anguille, and while we have good reason to believe that's not really the case that does give Mathilde a reason to think that the Druchii have some use for the Waystone network
Mathilde already thinks that Hatalath is hiding something related to the L'Anguille connection, and the probable lack of Waystones in Naggaroth likely only exacerbates Matty's suspicion. She might not know of Albion's existence, but she has reasons to believe that L'Anguille doesn't actually connect with Naggaroth.
Edit: ninja'd by Boney