After Subaru saved her from the Wolgrams she starts to develop feelings for him. Loving his kindness but she also understands his hopelessness.
Petra sees Frederica as her big sister. Frederica being her senior teaches Petra the basics of being a maid. Petra tries on outfits for Frederica and sleeps sometimes by her side. Knowing of Petra´s love for Subaru, Frederica supports her as she wants Petra to find happiness.
Petra works at Roswaal´s mansion as a maid. After the events of Arc 4, her relationship with Roswaal starts to worsen. Her cheeks would stiffen, tears would force their way out, she'd deliberately spill tea on his lap, not taking out the pins of his clothes and she wouldn't tell him when his buttons weren't done up. Roswaal, on the other hand, doesn´t dislike Petra, even standing up for her when she was accused of being the reason the mansion burnt down.
Petra respects Ram being aware that she is actually the one in the mansion who can accomplish the most but disapproves of her slacking off.
Petra sees Beatrice as her best friend. Doing various things to take care of her.
Petra thinks of Meili as a villain, not forgiving her for the things she did. But as a maid she still takes care of her, making her stuffed toys with Subaru.