There was something particularly relaxing about being in Petra's company. Bernadetta was used to being locked in her room, alone, thinking about her certain death during a training session, an outing gone wrong or worse, one of Professor Seteth's boring lectures. Anxiety and dark thoughts were a constant for her and she rarely took time for herself. Read her favourite book? Go for a walk and breathe some fresh air? Spend time with the people who made her feel comfortable?
(The last option was mostly because she was terrified of everyone, even the cats that hung around Garreg Mach.)
(Especially the cats.)
So Petra was obviously one of those people she was terrified of. After all, she was good at fighting and she liked to train with her classmates. Bernadetta had always been afraid that one day she would look at her and suddenly decide to challenge her – which meant she would have to run for her life.
Yet, one thing led to another and since Professor Byleth had taken over their class, Bernadetta had found herself spending more time with her classmates. It was something she hadn't been thrilled about at first (quite the opposite actually), but she had slowly gotten used to them. She had learned that Hubert was not the type to hide in the shadows and wait for the right moment to brutally murder him. She had also learned that Caspar's goal was not to chase her around the academy to break her in half.
And, even if she still found it hard to believe, Petra was not a spy sent to destroy her.
In fact... Petra was the one she had grown the most fond of.
She had shyly asked her to be her friend, then Petra had tried to teach her to hunt (again and again and again) before finally deciding to just spend time with her outside.
Bernadetta liked these moments. She didn't like talking to people as her words would end up reflecting her dark thoughts, and Petra wasn't the type to do small talk. So on the days when they decided to go for a walk around Garreg Mach or when they agreed to go on an errand for a teacher, Bernadetta enjoyed just spending time with Petra. And she liked to imagine that the feeling was mutual.
(Since Petra hadn't decided to use the excuse of the stray arrow to finish her off yet, Bernadetta dared to think that it was indeed mutual.)