Proteus Buff vs Sonya Debuff - Answer: Sonya is Dispell not Debuff

Short answer: no, Sonya won’t remove Proteus effect from enemies.

Long answer: Sonya removes buffs from enemies. Buff is a positive effect like increased damage, increased defense of healing over time.

Proteus puts a debuff in enemies. A debuff is a negative effect like blindness, poison, burning and so on.

Your enemy can remove Proteus effect of they have a cleanser - hero who removes debuffs from their allies, like Rigard or Vivica.

See this thread for more terminology explained: