Oh goodie, because I actually write a detailed summary of the story from the other people's perspectives (well, Dallas' was the most detailed) so that I can understand the relationship better and I just hope that it naturally comes out while writing - but of course not too easily - my editor figured something out too early and was annoyed I wasn't address it haha. So things can run the risk of being too hidden too ... I think my timeline of D & R's history is a bit hard to grasp so here's the timeline:
They meet around 18 -20 years old (I don't have an exact number in mind) but Robin is already forming a band with Owen and Sterling at this point, but it's not much to brag about. So D & R spend time outside of it and become friends. D is already crushin on R at this point. R is still crushin on S because she craves his approval, so she doesn't realize this, but she doesn't go to school and thinks D is cool. D isn't upfront about his attraction, partly unsure of her relationship with Sterling, partly believing that she was flirting back so it was mutual (she was, unknowingly), but also kinda scared cuz she's a big city girl. It wasn't very long until the scene where Robin gets kissed by Sterling for the first time. (S felt R slipping away and made some realizations that he didn't want to lose her.) And also where Dallas realizes that he actually totally missed his chance. Just totally. She is way too happy. And that's where it starts getting emo. A couple years go by, D & R are still good friends, but S gets the bulk of her time. D feels like he has to deal with the messes that S makes of her (this is where it gets real "nice guy" territory). So one night they're both drunk, R is particularly hurt, D is particularly done with giving a shit about S, and they fuck in a closet. D admits he loves her, R chooses to ignore this because her heart wouldn't be able to handle that. Next day R basically begs D to act like none of that happened. It was a big moment for him, a nothing moment for her (this is false). And that is when things officially spiral and where the flashback sequence R has while drowning. So when Dallas says that she's lying, he is referring to not only to her literally pretending she didn't know, but yes, unfortunately also since they met. To him, he's only ever shown her love, but that means R has really only ever seen a version of Dallas that loves with her, so how could she spot his love if, to her, he never showed it? She rationalized the sex as being for sex. She didn't quite enjoy it so it wasn't enough for her to flip her world upside down. So it was never going to work the way he thought it would. They both needed to go through some ugly.
As for your question on the proposal, that will be addressed in their open ended story once I'm finished with it. :)
EDIT: I found this excerpt from a scene I don't think made it to the preview in Open Mode...
"I felt like shit when we ... we let him go." "For years. I never got over it." "But did I write a single song about him? No." "I hid that sadness deep down. I buried it so well I thought I'd forgotten when I saw him again." "And then it was uncovered and so fresh every time he spoke." "Just the sound of his voice hurt." "I hid my feelings from the very moment I met him." "It must have been so frustrating to be so open, so in love with someone in complete denial all the way until what was supposed to be the end.
Beau's open mode ending is done, but I've been split between Emmitt, Seth and Dallas' path to finish after that. Maybe I'll focus Dallas now that I'm thinking about him.