I'm not quite sure what's with this hostility from you, Raineh. Everything is going to be fine and dandy. Fieri meeting and presumably joining up with the party is a foregone conclusion: she's where the party is going. Since the castle is notorious for being raidable by parties of adventurers, the entrance is almost certainly, if not open, then at least openable with only a modicum of effort. She'll trip the trap at the entrance, and either get stuck or be in need of help, and that's an excellent opportunity to roleplaying and building character relations.