Miss Skyler has done almost the same thing!!
She was literally having one more fit in my daughters bedroom one day, sounded like she was going to tear into something and rip it to shreds.. she was doing a "jackhammer" , barking and growling like crazyyyyyy.. I walked in to find my daughters mirror leaning against the dresser on the floor, Skyler was seeing her own reflection.

Funniest thing was... she would run around to the back of the mirror trying to find that strange dog that was invading her house!! LOL!!