I finally have a name for her, so here's the bio.
Marble is a side character in Bendy's Cartoon universe. She has a child-like, shy, and caring personality, plus she's helpful to anyone she meets. She is also a bit naive, so she can be easily tricked. Marble tries to steer clear of any danger that comes her way, but she's somehow in the middle of it all.
Her friends include Alice Angel, Cynthia Siren (her bio is coming soon), and Boris the Wolf. She doesn't like nor dislike Bendy although he tricks her regularly.