Mrs. Dilaurentis has many secrets. Her son, Jason, isn't fathered  by her husband but by Spencer's dad, Peter Hastings. After Alison "died", Mrs. D didn't seem to act like a normal grieving mom, she seemed up to something as if she was waiting for Alison to return. We've seen Mrs. D. handing clothes to CeCe Drake in secluded woods,

 

 

 

 

 

 

 

 

 

 

 

Sneaking around Spencer's house,

 

 

 

 

 

 

 

 

 

and keeping Alison's room exactly how it was before she left. Mrs. D wasn't always like this, however. She used to be kind to the four Liars, even offering Emily a place to stay (in Ali's old room---creepy). In the season 4 finale "A is for Answers", Ali reveals that after being hit in the back of the head, she saw her mother burying her alive.

 

 

 

 

 

 

 

 

 

 

 

 

What could this mean? Is she protecting Jason? I don't think so. I believe Mrs. Dilaurentis might be the one with the twin. The story Alison told to the boy she was babysitting could have easily been about her mother and Aunt. The clothes and older style applainces would totally fit into this theory.

 

 

 

 

 

 

 

 

 

 

 

 

Mrs. Dilaurentis' twin sister was sent to Radley for attemping to kill her sister. The night Ali was attacked, Mrs. D could have just found out that her sister escaped and was worried how she would retaliate, telling Alison to stay inside.

 

 

 

 

 

 

 

 

 

 

After Alison snuck out "that night" and walked home, Mrs. D watched her twin "kill" Alison and was forced to bury her own daughter alive. Now that the town of Rosewood knows Alison was never dead, Mrs. D killed her twin and buried her...revenge for forcing her to bury Alison alive. Not a perfect theory, but it could fit into the timeline.