Can you get electrocuted by using a water mist fire extinguisher for an electrical fire?

Yea the water conducts the electricity through the stream. The best way to put out an electrical fire is with a class c extinguisher.

However, fixed water mist extinguishers ARE used on high-voltage systems, with enough clearance to avoid arcing, where the safe design is done according to NFPA 750 Standard on Water Mist Fire Protection Systems.