Clues Mona was A →  2x13

Clues Mona was A →  1x10 & 1x13

Clues Mona was A →  1x06 & 1x09

Wizard of Oz references

Clues Mona was A →  She was always texting!

Clues Mona was A →  2x16 & 2x25

The final clue, and how Spencer figured it out.

Clues Mona was A →  2x16, 2x24 & 2x25

Clues Mona was A →  2x24

It obviously wasn’t Melissa (because when are the PLLs ever right?) so that left Caleb or Mona.

Clues Mona was A →  2x19

Now we know what Mona’s third personality was.

Clues Mona was A →  2x19 & 2x20

Clues Mona was A →  2x17 & 2x18

Clues Mona was A →  2x16

A strikes right after Hanna and Mona have a fight

Clues Mona was A →  2x15

Clues Mona was A →  2x13

Clues Mona was A →  1x16 & 2x10

Mona must have learnt French recently, as Hanna was surprised to hear her speaking it.

Clues Mona was A →  1x09 & 1x13