I can't imagine what those "reasons" could be, considering all we are told of "Lethe" in "Dagger Of The Mind" (TOS) is:
ADAMS: Lethe came to us for rehabilitation and stayed on as a therapist—and a very good one too, I might add.
LETHE: [blankly] I love my work.
ADAMS: [gesturing to Kirk] Go right ahead, Captain.
KIRK: [to Lethe] Before you came here?
LETHE: I was another person. Malignant, hateful.
KIRK: May I ask what crime you committed?
LETHE: Does it matter? That person no longer exists.
ADAMS: Part of our cure, if you will, Captain, is to bury the past. Why should a person go on living with unbearable memories...
Adams' "neural neutralizer" does seem rather similar to the Terran "memory extractor" Section 31 was going to use on Spock, too.
I'm not saying they've ever necessarily intended Cornwell to be her, but it's certainly within the realm of possibility.
-MMoM
Well, looks like we now have good evidence that Cornwell isn't Lethe...
