I think maybe try stopping the top ups too. See how often she asks for milk without the top ups, and if she feeds more often that's a good thing as it will tell your boobs to make more milk and in a short while (ideally) she will be getting all she needs from your boobs. Alternatively you could still express after feeds, or every other feed, to help boost your supply but don't give it to her- freeze it for a 'rainy day'.

75th percentile is amazing- doesn't that mean she's bigger than 'average'? So it hardly sounds like she's struggling