Spencer Hastings Could Absolutely Be "A.D." on Pretty Little Liars, and Here's Why

In a season six dream sequence, Spencer finds herself in Radley Sanitarium. She chases a little girl through the halls and watches as she dances in a dusty, abandoned room. With her long, stringy dark hair, it's hard not to see this young girl's resemblance to Spencer. The dance paints a picture of a dark past, perhaps a suppressed, traumatic memory of Spencer's. If Mary was in Radley and Spencer is somehow related to Mary, is there a chance Spencer was there too, when she was very young?