That kinda is Gwen's yandere mode.
Her original personality, plus what you did to her, she's very clingy.
If you don't have sex with her at least two times a week she starts getting more and more crazy.
If you don't have sex with her for like a month or so she gets to the final stage.
Not much more than that, but don't worry she won't kill or harm anyone, that would upset the MC and she's rather die than upset the MC.