Well in all candor I think the way for you to feel better is to skip the complaint.

If you file a complaint, this matter will be with you for a long time. It will continue to draw your attention as relevant procedural deadlines approach. You will go over and over the incident in your mind and on paper. And, in the end, as others have said, the T will not be disciplined for this error, further compounding your frustration.

Forgiveness doesn't mean listening to her side of things. Her apology says that there is no "her side", she screwed up and she admits it and is sorry. Forgiveness means accepting her apology and letting the resentment go. That is the way, in my opinion, to feel better in this situation.

I'm sorry that the psychiatrist made jokes about it. Being forgotten isn't funny. That's one reason that the therapist apologized.