Chance for Mathilda to not join bb clan
While he didn't say anything, I would say it is 0 chances of that not happening. Sonja left the BB to join the WW, so someone has to take her place, and that someone is going to be Mathilda.
She fights for her own freedom and other clan members, in that I believe Nox was wrong. It made me respect Katja. Though, staying to close to Candrid will corrupt her so even though she is not evil right now, I believe she will turn into one. Btw, Katja has something with the attack to the village which makes her at best, opportunist. So even if she is not evil, she is on the fence.
What Candrid did is what Vikings would do at that time, I can't see why Katja wouldn't get behind her for the opportunity to free the DR and to get the Outcasts a better life.
Katja is the leader of the Outcasts, so they attacked the village on her order. The attack was made to weaken the leaders of the BB and DR clan originally, but Candrid betrayed Torsten and made the WW get the brunt of the attack.
Now Candrid is the leader of the BB and is in an alliance with Katja, who is leading the DR and the Outcasts, and Mathilda, who is probably going to bring some dissidents from the WW to the New Alliance.