|“|| Spencer: I feel like we're just starting to get to know each other again.|
Melissa: Me too.
— Spencer and Melissa
They have a love-hate relationship. Sometimes, Spencer isn't sure if she can trust Melissa because she is somehow always connected to Alison's disappearance. Melissa is also a popular suspect by The Liars of being on The A-Team in several seasons. They fight a lot but sometimes if it is very serious they can count on each other. After all they are still siblings. When Spencer was in elementary school a bully named Kendra Santoni "made Spencer her personal punching bag" as said in My Name is Trouble, and one time Spencer came home with red marks on her chest from being slapped with a jump rope. She was to scared to tell her mother, but Melissa saw the marks, and told Kendra that if she hit Spencer again she would make Kendra eat that jump rope. Most of their fights are about Alison DiLaurentis, Garrett Reynolds,The A-Team with the huge fights regarding Wren Kingston and Ian Thomasl Their parents would often side with Melissa.
Melissa and Spencer would return from a strategy campaign, regarding Spencer's interview style, to the barn. After an exchange between Spencer and Caleb, Melissa would question her regarding her status with Caleb. Later on, Melissa would be helping at a booth while Spencer would have an interviw with Damian regarding young people's voting. Later that night, Spencer would find a freaked out Melissa; she would explain that while doing an interview the mood changed after Damian got a call. She would question Spencer to see what she did with the tape, regarding her confession of burying Bethany, before quickly going up to her room. (The Gloves Are On)
Melissa is mentioned by Mary when speaking to Spencer and a picture is shown of the two girls. (Tick-Tock, Bitches)
Melissa [in Pilot (1.01)]: I was hoping you'd be happy for me.
Spencer: Well, you know what they say about hope. It breeds eternal misery.
Spencer [in To Kill A Mocking Girl (1.03)]: I made some pasta if you're hungry.
Melissa: I'm not eating pasta. I don't wanna be depressed AND fat.
Melissa [in Keep Your Friends Close (1.10)]: I actually had a good time with Ian.
Spencer: Wow. I will alert TMZ.
Melissa [in Will the Circle be Unbroken? (3.22)]: Spencer, what happened?
Spencer: How far back do you want me to go?
[Melissa starts crying]
Spencer: Right. I'm in a psych ward and you're the one crying.
Melissa [in Face Time (4.04): You don't understand! You've never understood! I've been protecting you since it started! Since before it started!
Melissa [in No One Here Can Love or Understand Me (5.11)]: Goodbye Spencer, I love you!
Melissa [in The Gloves Are On (6.13)]: When did that happen?
Spencer: What? Caleb? We're friends.
Melissa: Really? Cause I know how you like to shop out of other people's carts.
- Spencer has either dated or had flings with two of Melissa's boyfriends in the past. They are Ian Thomas and Wren Kingston.
- Melissa moved into the barn in Season 1, even though Spencer was promised the barn.
- Melissa was unaware of Spencer's adoption and thought they were biological sisters.
- They are actually half-sisters, as they share the same father but different mothers. They are also adopted sisters since Victoria and Peter adopted Spencer.
- They share a half-brother, Jason DiLaurentis.
- At the beginning of 'Til Death Do Us Part, they were starting to form a relationship with one another again.