After Kahglia told her about true magic and she learned that Toz was already about to learn it, Red Hook didn't feel like playing around anymore. She had her dagger, the Blood Ancestor's old dagger, and although it had lost a lot of power and was in a mostly dormant state, it still helped her deepen her understanding of blood magic.
And as she thought about it, Red Hook realized that Toz's guess about the blood-ruling attributes it granted her being true magic might not be empty words. If the Blood Ancestor was as powerful and great as Kahglia and the Blood Demon claimed, it was very likely that he had mastered true magic.
If the Blood Ancestor had indeed mastered True Magic while still in possession of the Bloodletter, Red Hook found it very reasonable to assume that she would reach that level as long as she continued studying the legacy left behind inside the dagger.
Maybe a little boring, but we're getting close to the Transcendent Realm, so bear with it ;)