I have to disagree with you here. Jamie loves our MC more than anything, but our stupid MC doesn't see it. He's the problem, not her! Trevor puts it so succinctly to her: "Why do you let him treat you like a little sister?" She has to go because otherwise she would destroy herself. His reaction to her revelation that she's leaving is not what she would have expected. He was really happy about her great job offer. There was no sign that he would miss her. He doesn't see her as a woman to love yet. At some point he will also realize that there is someone missing in his life. The question is: "When will he realize it???"
I agree with what you've said with the added proviso that the crux of what we're talking about is the difference between platonic love and romantic love.
Jamie/Rockford share a deep platonic love that Jamie yearned to develop into romantic love. By the end of Ep 4, Jamie made a decision that would, at minimum, pause any possibility of romantic love developing in the future. That doesn't suddenly erase the deep platonic love they already share.
Rockford, on Jamie's path, realizes too late that his feelings for Jamie extend beyond platonic love. When not on her path, it's far less of an issue because Jamie has more or less already come to terms with the fact her relationship with Rockford will only ever be platonic.
Thus, Jamie has decided to move on by the end of Ep 4, even although she still seems conflicted about it when we last see her. This is where the "Dwant" comes in. She is moving on from the hope of a romantic relationship with Rockford while remaining conflicted enough to seemingly feel jealousy when seeing Cassie around Rockford. Then again, maybe Jamie knows some things about Cassie that we don't, so she is merely being protective of Rockford, her platonic friend (that's not my interpretation of it, but such a scenario is always a possibility, that's up to Impious Monk).