Monily is the friendship pairing between Emily Fields and Mona Vanderwaal. The two had known each other since before the events of The First Secret, but didn't become friends until Taking This One to the Grave. Due to Ali's dislike for Mona, the two didn't talk all that much and only began to once Mona was popular alongside Hanna.
The relationship between Mona and Emily started out under bad pretenses, as Emily was friends with Alison DiLaurentis, Mona's High School bully and tormentor. Emily often stood by as Alison bullied Mona, never intervening or stopping Alison. It wasn't until later, when Hanna, Emily, and the other Liars became friends again, that Emily and Mona started interacting once more. This time, it was friendlier and more helpful; Mona even helped Emily get back on the swim-team. After Mona was revealed to have been A, and the one who tormented and stalked Emily, she never fully trusted her again. They briefly became friendly again before Mona's mysterious "death", and helped one another escape A's Dollhouse. Mona later helped Emily find out who performed the insemination procedure on Alison, which brought the girls a little closer, until Mona was revealed to be Charlotte DiLaurentis' killer. The two are currently friendly for the sake of Hanna.
Pilot Aria asks Emily if that's Hanna, as she doesn't recognize her at first due to her make-over. Emily informs her that Hanna is the new "It-Girl", and then points out Mona, informing her that the two are best friends now.
Misery Loves Company Emily is in her car outside of Rosewood High School, waiting for Caleb as she had plans to follow him. She sees Mona exit the school and watches her for a moment. When Mona looks in her direction, Emily crouches down in an attempt to hide, and Mona has a hard look on her face before she smiles and joins her friends. Emily watches Mona sit down at a table with a group of people, and then leaves to follow Caleb.
Under The Gun Emily confronts Mona during lunch, and tells her that she wants to know what A has on Toby. Mona comments that everyone like to know, and Emily tells her that she wants in. Mona doesn't understand what she wants in on, and Emily tells her that she wants in on whatever it is that Mona is doing. She lists things that Mona knew or was ahead of, and says that she has the fast-track on A while everyone else is lost. Mona sighs and admits that she isn't the one pulling the strings anymore, and that everything that they've both done, A has proof of. If they make one wrong move they all go up in flames, and Emily walks away a few seconds later. Cover For MeMona is pulling out of her garage when she notices that Emily is directly behind her. She slams on the breaks seconds before she could hit Emily. Emily walks around the car to the drivers side and states that she needs to talk to her, and Mona curtly says that she has somewhere to be. Emily asks if she's meeting with Ezra Fitz, which both surprises and annoys Mona, and she tells her to get in. Once Emily is in the car, Mona admits that she's surprised that it took her this long to figure out that she is working with Ezra. She admits that she thought it would be Aria, and that Ezra should have told her about the book a long time ago. Emily asks her when she found out, and Mona admits that she's known for a while, and found out around the time that she bought Jenna's car. However, she didn't want to help him with the book, she wanted to stop him or at least stop the parts that included her. Some of the things she did she could still go to jail for, so the pair made a deal. She would tell him about her exploits and he would edit out anything she did that was illegal. Emily asks if she's read the book, and what it says about Alison. Mona admits that she hasn't read Ali's parts only her own, but if Alison were her she would probably love being a part of a scandalous page-turner. Emily asks if the only reason she dated Mike was get to close to Aria, and Mona seems saddened about this. She states that Mike is a really nice guy and that she did fall for him, but when the Liars started catching on she told Ezra she wanted out, but he told her that getting out wasn't an option. She didn't want to drag Mike into her mess so she broke-up with him, and Emily asks if she really went through all that and got nothing. But Mona insists that she got something, something merky but big. She asks Emily if she remembers after the Lodge fire when she told them all that someone stole the game from her, and Emily says that they thought it was CeCe Drake. Mona admits that she never found out, but whoever it is, Ezra thinks he knows.
- Emily stood by and watched as Alison bullied Mona, which lead to resentment on Mona's part.
- Mona helped Emily get back onto the swim team in "The Naked Truth".
- Mona tortured Emily as A, although she tried to make-up for it later after being released from Radley Sanitarium.
- Mona told Emily that she wasn't the on pulling the strings anymore, and warned her to be careful.
- Emily and Mona were both held captive in A's Dollhouse together, and helped each other to escape.
- Mona has known of Emily's real feelings for Alison, and had known for a long time.
- Mona helped Emily find Alison's sperm donor and the clinic that performed the insemination procedure.
- She knew that Emily was in love with Alison.
- While searching for Emily and Alison's sperm donor, Monily pretended to be a couple in order to get information out of a doctor who worked at the clinic that performed the insemination procedure.
Emily: Mona... I know that you heard what Tamborelli said to me. And I'm not proud of the stuff that went down when Alison was still here. She treated you badly and I... I let her. I never tried to stop her. And I should have. I'm sorry.
Emily: Mona, wait. I can't blackmail a school official.
Mona: Honey, you can't be a shark if your toothless.
Emily: Why would you do this for me?
Mona: It was fun. It's what friends do. But now, you gotta help me. What do people wear to a swim meet? If I show I up in my wedges are they gonna get mushy?
[Both girls laugh]
Mona (to Emily): You always were the weakest link.
Emily (to Spencer and Aria): Think like Mona. Just for a second.
Mona: You can tell Ali you love her in front of me, Em. That hasn't been a secret since we were in Brownies.