I've gotta say, I really hate this part of the writing. It's too painful and contrived. Jamie has loved this guy since she was literally a kid, and is perceptive and smart enough to know exactly who he is, and has learned a lot of why he is that way. She gets her perfect job offer just as she's possibly reaching a point where her dreams of a romantic relationship with him is actually possible, and he opening up enough to maybe let her in, all at the same time. There are no good choices for her.
Psychological healing is never linear. You may hit that cathartic realization, but it takes a lot to make permanent changes in behavior patterns, and there's always cycles to patterns. Even if he opens up doesn't mean he won't retreat back inside. Just because they start a relationship, it doesn't mean it will succeed. Just because she loves him, doesn't mean she will sacrifice her goals. BUT she's stuck with the aftermath either way.
This Harvard opportunity is too good a job for her to have just come along right now. The only thing that makes sense, outside of bad writing, is that the position was opened for her intentionally, to both advance her career and get her away from the MC. Her father and his people are definitely able to pull those strings, and has the motivation to do so, but we haven't seen anything to hint that.