Just as Bronya's being surrounded by the enemies, Seele, the backbone of Wildfire arrives just in time to save her but immediately turns to confront her after.
In the end, Seele finally reveals her reason for being there: Oleg, leader of Wildfire is asking for an audience with the noble girl from the surface.
Naturally, you can't pass up on this opportunity to get in touch with Wildfire. Follow Seele's instructions and head to the Great Mine.