Considering she's still only 15, I'm praying to God that she can be redeemed somehow. Poor thing never had her ass whipped as a kid and was never told no. But also, I called it. She's a yandere.
I'm rooting for her 100%. I love me some toxic yandere types. I hope when they reunite she cries and apologizes and tries to get him out of the underworld and he accepts her.
My only problem with this type of character in this type of story is that they're often way too easy to escape from. It's way more interesting when they're good at manipulation. Shout out to Yuno Gasai we need more characters like her.