Oh Come On

I know Trixie apologized in the end of magic Duel, but that doesn't mean she doesn't still want to prove herself and be the best magic user out there; she just wants to find a legitimate way of doing it, using her own skill, learning new magic.

Showing Twilight she can be just as good.

Of course now Twilight is at a level of magical power that Trixie can never hope to attain; poor Trixie.