With everything we know about A, I could only come to one conclusion: Jenna is Big A. My arguments for this theory:
1. Season 2 finale (Unmasked): It’s a theory that Jenna met Shana in the park that day before the Ball since they meet in the Season 3 finale at the same spot, but what if she was actually meeting Mona there that day? There does seem to be a connection between Jenna telling someone “You know what you need to do,” and Mona telling Red Coat at the end “I did everything you asked me to.”
2. During “that night” (the night “Alison’s” body was stolen), Jenna was seen wearing a red coat and black gloves. I don’t think this was a coincidence. I think nobody pays attention to this since Jenna gave an “explanation” of this to the Liars.
3. The Jenna Thing: Enough said.
4. Marlene says that A’s motive is love: Jenna could still be in love with Toby. It is said that Spencer is A’s main target. This would explain why.
5. Speaking of Toby: Ever noticed that when A writes a note by hand, she always capitalizes her Ts? T is for Toby! (Possibly A’s motive?)
6. In the season 3 finale, A saved the liars from the lodge fire. In 4x01, Jenna has a burn mark on her hand.
7. In season 5, A returned in the same episode that Jenna returned.
8. The group known as “The Alliance”, consisting of Jenna, Shana and Melissa were supposedly protecting the Liars. But Shana turned against them, Jenna could have too? Were they really protecting the Liars?
9. The mask that A always wears, has one solid eye. A is thus half-blind while wearing the mask. Is that a metaphor for Jenna’s blindness. Also, the solid eye is green. Is it possible that it’s also Jenna’s eye colour?
I know however, that there are arguments against this theory:
1. Jenna is blind. BUT: At the end of 1x02, we see that Jenna can still send a text message, even if she is blind. And this might sound cruel, but is it possible that she is faking being blind right now? (I think that is unlikely, though)
2. Jenna and A were both at Wilden’s funeral. BUT: Is it a coincidence that A chose to sit right behind Jenna at the funeral? I think this A might have been a decoy. Remember: she gets into a town car and drives away after the funeral; Holbrook corners the Liars and says they just want to find out “the truth”. Immediately after that, A tells the Liars that “the truth will not set them free”. How did A make that connection when she already drove away... unless she was still there? Also: Is it a coincidence that after “Alison’s” funeral, Jenna also got into a town car like A did after Wilden’s funeral?
3. A blew up the Cavanaugh house (and I think we can assume that Jenna was living there in 5x05 since Aria found her crying in that house). BUT: I think it’s obvious that Jenna was not in the house when it exploded. Is it possible that she figured Toby would either be in the house or run in to save her or his dad? The house also exploded for the second time while Toby was in or near the house. I think she blew up that house in an effort to hurt Toby.
4. A is assumed to be a blonde woman. BUT: I think it’s obvious at this point that A might possibly have dark hair, because we see the blonde wigs in her lair in 4x01.
5. If Jenna is A, why isn’t she punishing the Liars for killing Shana (who she was said to be in love with)? While holding the Liars at gun point, Shana said that Jenna did not know she was there. When A returned later, Aria’s biggest fear was that A knew that she killed Shana. But A has not mentioned it yet: because A does not know. The closest A came to mention it was after a drunk Hanna mentioned New York to Sydney and even then A did not put the pieces together, which also means that either Sydney is A or A heard about the New York secret from Sydney. And who is close with Sydney? Jenna!
I would love to hear your thoughts on this crazy theory. It's the only thing that makes sense to me...