This way of looking at things is debatable, and Ellen herself is inconsistent about it.
Which I consider realistic. I don't think a person would be in Ellen's shoes and not be inconsistent about how much ownership they feel over some of their memories. I think their feelings about the same memories could change based on mood, why it's been brought up, etc.
Which is how people tend to be, but I wanted to point out that Ellen is intentionally inconsistent about this, and that I'm not forgetting some official "Ellen feels this way about Elliot's memories at all times about" rule I'd written at some point.