She is actually a decent adult, she wanted to have date as an excuse to get rid of the hierarchy they ought to have as an employer-employee inside the coffee shop.
Once in the date she makes him realize his feelings are those of trust and respect and not love, he was misguided into thinking that falling in love with an older woman would make him "normal".
He opens up to her about his assault and confides that he feels as afraid and hurt as he did back when he was assaulted, and his inability to move on and be normal makes him hate himself.
Rio retorts that "being normal" is not something clearly defined, she puts herself as an example, she doesn't want to engage or get married, and people tend to think she has a trauma or a reason to avoid commitment when in reality she doesn't see a reason to do so, so she rejects this assumption of being normal as a good thing.
She tells Mc that "normality" is something he should define by himself, based on his experiences, letting go of his pas or embracing it, it doesn't matter if it is "normal" or not
Mc questions if she isn't afraid of being different to everyone else.
She answers that she doesn't care since she is and adult, but for him it shouldn't matter he is not an adult yet, he is just getting there, its ok to be anxious, and afraid, it's ok to make mistakes, being eager for a quick "normality" is a trap he should avoid, since true "normality" is something much more important and it is a long road he must take to achieve it, whatever happened to him, wasn't his fault, the abuser was at fault, no matter what people say to him, he must remember that.