Second exchange was in class where she let's mc believe she had a bf, there were a couple moments where there were little things in between that and the quinn stunt. Watching the movie she basically tells him not to catch feelings. But all that leads to her almost slipping up about josy when she's mad at her dad. Which again should of told mc if he had listened (it was pretty obvious). But all in all its not that she's completely innocent, just "honest" sooner as far as actions than josy.
Maya also cheated in her action. Namely Josy. Both of them cheated on this point. You could see that at the end of EP4 when MC revealed everything.
What is important in all these entanglements is the reason why they did it. And I think that was made quite clear.
They both felt alone and thought that their relationship was actually over. And suddenly the MC appears and gives them what they are missing. The feeling of being wanted, of no longer being alone with all their worries, someone who shows understanding.
And there are two kinds of people, in terms of trust. The type of person (Josy) who gives everyone an advance trust and the type of person (Maya) where trust has to grow.
And one thing must not be forgotten, they are still teenagers. Think back to your teenage years and the mistakes each of us made at that stage of our lives. (At 18/19 you are still a teenager).
I suppose that's what DPC wants to portray.