I find it hard to believe that she's a Kenobi. Obi-wan was probably 60-ish* when he was killed and adhered pretty close to the Jedi Dogma, so it is unlikely that he had a child. Plus, since he was 40 at death, that would make any child he did have pretty close to Luke and Leia's age. At closest, she's a granddaughter (unlikely), but if she is a Kenobi, she would probably be a niece.
What we don't know is if the Council had some kind of reproduction program or something. Either a eugenics program where they select two compatible Jedi to breed better Jedi, or they just take biological samples of each Jedi to work with in the lab (a la Boba).
I still think the Skywalker (either Luke or Leia) connetion is the most likely option.
*Figuring he's 25 when they discover Anakin, 40 when he becomes Vader, and another 18 years for Luke to grow up.