I’m trying to decide what training Brianna goes through to learn how to use her powers. I know it’s going to take her quite a bit of time to get used to a new form (though the more she transforms into one particular animal, the more she gets used to moving around in that particular form), but irregulars are pretty rare, so only a few doctors know of their existence (Brianna was very lucky to find a therapist who knew of Irregulars’ existence). Also, does anyone have any idea as to how to work mind reading into a mystery story without making it obvious who the killer is? I want Dalton to be a mind-reader in the series.
A classic trope is for her to find a mentor who has the same powers (think about Yoda from Star Wars or Morpheus from The Matrix). That mentor could teach her how to use the powers and also warn her of the dangers. For a specific animal-morphing training, watch The Sword in the Stone to see how Merlin trains Arthur.
Make the power very chaotic or unreliable. Maybe Dalton sees too many people's minds at once and can't tell who is thinking what. Or maybe Dalton reads thoughts, but can't tell the difference between people's actual intent and their thoughts, dreams, or even memories of movies they have watched.
Make the mind reading power be a swirl of thoughts that takes time for Dalton to sift through.
I say take the spider-man approach and let her learn on her own making mistakes along the way and how those mistakes affect the world around her.