To be honest, Mary is actually my favorite character. The reason why is because I don't think she intended to KILL Garry, she wanted to leave with Ib because (in the game when Marry starts following you around after stabbing the head, she'll say "I've always wanted a girl like em to be my friend" and stuff like that 
) she wanted a friend and she wasn't very fond of Garry because he found out she was just another painting by Guertena. She was lonely and she was locked up in that world for who knows how long. Never aging, can't eat, drink, I don't even think she could sleep so she went a little crazy. But trust me, if you were locked up like that, you probably would've lost it as well. She just wanted to go outside 
And I don't know how, but I feel like I can relate to that That's clearly why she's my favorite :3
) she wanted a friend and she wasn't very fond of Garry because he found out she was just another painting by Guertena. She was lonely and she was locked up in that world for who knows how long. Never aging, can't eat, drink, I don't even think she could sleep so she went a little crazy. But trust me, if you were locked up like that, you probably would've lost it as well. She just wanted to go outside And I don't know how, but I feel like I can relate to that That's clearly why she's my favorite :3