I think the story would be more enjoyable if you mixed up the paragraph structure a bit. Try not to always start with dialogue.

i.e. Every once in a while, make it more like this:

Sylvie mindlessly twirls a finger around Graham's curly locks. "You still bite your fingernails, and you still get pissed easily. So, there's no way you can be Mister Perfect and still have those… issues," she comments, only looking at him when she says the word "issues".

Though it seems more like part of a longer story than a one-shot, I liked how the characters interacted. It's adorable how loved Sylvie is!

Interesting beginning. I feel like Graham is iffy, but I'll have to wait :)