In her defense, she's only implied to have a romantic thing for her, though it could be argued she only wants to be platonically involved and is just super possessive. After all, she didn't say that she fell for her, but for her delinquency which implies she's not romantically attracted but is more wanting to be her number 1 protege.
Though if she devolves into a yuri NTR ship, I will riot.