Hi! @seoulyramen, so my first speculation is that she does remember but it doesn't even occur to her that he would remember her, especially as she is in her older state. I am thinking that maybe the other times she saw him, he didn't say his name? Although, I would really like some more info about the other 2? times they interacted and she "ignored" him. Afterall, we are seeing this through his eyes, so maybe there is more to those stories as well. But, yeah, that is the speculation I prefer. In this case, I also feel like that is why she was interested in his clothes in the first place.
My second speculation is that maybe he had a different name in his youth? I mean, E Do isn't really a common name I have heard in any other dramas. It has a kind of make a name for yourself feel to it. I am less convinced of this one, but there is some validity to it because of his family issues.
Either way, I think it is safe to say she at probably doesn't remember him saying that she is his soulmate, otherwise she would have at least known who is first love had to have been.