She's not thinking about rubbing the om in your face. She forgot that she had requested that you drop the mail off to her, thus the om being there. I'm sorry you had to see his car there. It does hurt and yes, it also can make you angry as well.
Yes, their memories are that bad. It's the depression that has made their memories mush pudding. They have a great way of compartmentalizing things and can function fairly well in day to day living, but there are times when the confusion sets in and causes memory lapses. At times, we aren't the only ones that see the facade cracking.
Her journey appears to be the typical one mlcers make. I'm sorry your day started out the way it did.
Hang in there!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.