Okay so she still killed him, just not in the specific way Palpatine wanted. So she won on a technicality. Not really a huge victory for her character though is it?
Failure would have been using the dark side or becoming a Sith, etc. Jedi’s are not pacifists. They all make their own personal handheld decapitation machine. So yes, melting Palpatine’s face off, accomplishing something even Yoda could not do, that’s a huge victory for her character. From scavenger to savior of the Jedi Order.
Pacifism is clearly the Jedi ideal. I actually think Rey finding a way to set aside her lightsaber would have been a better resolution, and a more interesting path for her to take the Jedi order in.
Simply being able to kill the big bad guy is terribly unimaginative and un-meaningful as a victory for the character and for the Jedi as a whole.