I think that the concept of an amnesiac super heroine works better as a sitcom.
30 minutes episode in which she must save the world. Every day her friends have to convince her that she is a super heroine and she has super power. Obviously she initially does not believe them and think that THEY are crazy. Because she will use her power when she is in danger or sense somebody she cares is in danger, her friends have then to do all sort of things to force her to use her power. Once convinced that she has super power, instead of trying to save earth, she could be very shallow and try to abuse her power (shopping, …).
She needs to have a kryptonite that the heroine would be attracted to: Cake, red shoes, …
Using the usual sitcom archetype characters:
The square: she is the square character or the personality she has are.
The wisecracker: slacker who uses the fact that she is amnesiac to not pay his due and financially exploit the situation. Maybe a family member, a brother/sister/cousin.
The bully: the stupid baddy who tries to take over the world and always fail. The baddy secretly hope that they would be BFF. Most of his plan then backfire against him/her.
The Dork/Geek: the one who tries to solve the solution. Has read all the books on amnesia or personality disorder. Usually knows the answer, but nobody listen to him. Often save the day, but somebody else take credit for it.
The Goofball: the out there character. Think Phoebe in Friends, Kramer in Seinfeld, Daphne in Frasier.

I agree with most points that DPG made, but I have a question. Would you put the reversal of fortune in the logline? Because if you do, you have a lot to cram in less than 30 words.

I also think that the proposed changes to the story results in change to the kind of person the main character is. I am far from convinced that the changes are realistic. When it was originally about a down on his/her luck teacher, we now have a CEO. I would expect the behaviour and the dynamics between characters to be completely different. CEOs tend to have belief in themselves and a ‘Can do’ attitude that most teachers don’t.
So I went back to the original logline.
Without the reversal explained I have in less than 30 words:

When a desperate destitute teacher sympathises during cancer treatment with a lonely former mafia hitman, she must convince him to kill her so her family inherit her life insurance.

With the reversal or at least a hint of the reversal, the logline is way too long. Here is my attempt:

When a desperate destitute teacher sympathises during cancer treatment with a lonely former mafia hitman, she must convince him to kill her so her family inherit her life insurance or to kill the loan shark who preyed on her and her relatives.

At least now, the introduction of the hitman does not lead to more questions about money. And the character is back to be a down on his/her luck teacher.