Since Dolly is technically mute and only can speak a word I believe that maybe to communicate she might have picked up some sign language and if Olivia and her ever got close, she showed Olivia some sign language to understand her, but Olivia just wants Dolly to teach curse words:
Olivia: So you’re saying that wait I mean you’re signing that only half the population knows sign language?
Dolly:*Start using sign language to say: Well yes it’s because some people find it difficult to understand it but my mom wanted a way to communicate with me and also I wanted to communicate with her. I hated the raisin bran cereal that she bought for me I want Lucky Charms.*
Olivia: That’s cool. Can you teach me some?
Dolly:*My first Dolly is excited, but then realizes what Olivia intends to do and then starts signing saying: You just wanna learn curse words, right?*
Olivia: Yeah it’s because Donna is trying to limit my curse words so she made a swearing jar, even though she swears as well, but is not fair…
Dolly:*First start thinking and then gets an idea and then starts signing saying: All right I’ll teach you one, but I won’t do it for free*
Olivia: OK, fine name your price.
Dolly:*Smiles, and signing saying: Two bags of pipe cleaners, but the glittery kind*
Olivia: Ok fine now teach me a word.
(Later that day after Dolly went back home, with her new bag of pipe cleaners Olivia wanted to test out her sign language that she was taught I going up to Donna)
Olivia:*She’s saying in sign language: What’s up bitch?*
Donna: Swear jar now!
Olivia: How did you know what I was saying in sign language?
Donna: Olivia my sister Susan has been teaching me sign language to communicate with Dolly whenever she dropped her off here anyways hasn’t she told you I’ve been doing this for weeks?
Olivia: Dammit I wasted my allowance on pipe, cleaners for no reason!