Marielle is an acquaintance to Chise, who after meeting, helps in various ways, offering to pay for the Dragon, that Chise wanted to take back to its rightful home and trying to fix the girl's Dragon cursed hand.
Marielle hasn't interacted with Ainsworth much, it not being neccesary to her. Whenever Ainsworth is in Marielle's presence her main focus in on Chise. Ainsworth and Marielle are neutral towards each other.
Phyllis has taught Marielle since she was very young, teaching her how to become a Witch in her coven. Phyllis is a mentor and motherly figure to Marielle.