Leave it to the AikiWeb community to extremely over-complicate a simple point!
Yes, she could also have been an alien from Mars, secretly out to infiltrate humanity, and Aikido was just her backstory. You never know! I also find that highly unlikely though.
Simplest conspiracy is that she is an alien here to bestow the secret Ki stuff to a Sensei who has not found it from anyone in his search yet....
First he has to demonstrate he is worthy by spending countless years taking her through basics up to Shodan before she reveals that all the while she was testing his character...
Try to throw in a romantic angle if you can with some more intrigue and I can get you Mini series on HBO or Netflicks.