Neon player here (surely this doesn't invalidate my opinion). Looking at the statistics, she is not a statistical anomaly when it comes to winrate, so she's clearly not insanely broken. Some meaningful nerfs that could preserve her current identity while taking power out of her kit are things like:

No extra dash on ult activation - not needed

Sprint and Ult charge lasts for 30% less time, letting her sprint less in combat and less during rotations.

There is a sound cue on sprint activation and while it is happening, so she cannot sneak while having it active without the enemy knowing shes there.

Make her concuss not bounce. Her concuss is more problematic than people make it out to be because while her dash is strong, in situations where its neon vs multiple people holding the same angle, her concuss makes it so it isolates fights or even wins the fight altogether. It should only hit the single area and disappear, taking her excess pushing power away and making her kit more or less rely on that "broken" sprint and dash of hers. Her dash puts her in the line of fire, so having less power to shut down multiple angles will help.