Lydia Winters
Lydia will be having dreams about her life with Higgs (some more scandalous than others) and when she awakes she will remember her other life. Later in the day they will fade and she will wonder if she is forming some sort of crush on Higgs and that would freak her out. However the more dreams she has the more confident she is it isn't that and something is very wrong.
Also as she walks around familiar places like Diagon she will have flashes of what the town looked like during the war.