Same. She could have just ended her friendship with Titania but she decided to shut herself off from the world so I hope there's a solid reason behind this.
I doubt it affected Fern that much. Being the asshole is his natural personality trait. Most of his actions in-game are 99% player's fault. According to Miss Direction's prophecy Fern would be the one saving Reborn in our place, but ever since we've survived train bombing we've been constantly triggering his inferiority complex to the point where he decided to join meteors and raid Amaria's mansion just to get back at us. Defeating his sister would only be an icing on the cake.