The interpretation I heard was that she was essentially not only converting to worshipping Jesus’ father, but also denouncing her old religion.

The Canaanites specifically were essentially enemies of God, and are all descendants of Caine*. So basically they are the exception to the rest of the world, and that’s why she had to unusually defenestrate herself to receive the blessing.

Jesus does help non-Jews in other instances without such hesitation in the Bible.

*From what I remember at least