The most painful thing in the world would be you being hurt because of me. I'd never want that. [And that is the honest truth. It IS awkward and painful, without question, but he understands and accepts that she can't tell him why, can't even tell herself why. Without memories, they're shapes without containers, no reason to tell why they are the way they are.]

[But an idea hits him.]

...this might be a little forward, all things considered, but -- are you such a flirt maybe because it keeps people from getting to know you? Who you are deep inside?

[It makes sense, doesn't it? If someone who got to know her hurt her badly in the past, maybe the source of that pain in her chest is a fear of what someone getting romantically more involved with her could do again.]