Two crimples in that theory: She said boys which means not her, and even if she did I don't see her with a Pokemon a la Ash's Mom's Mr.Mime. Not even a mention about it from Oak himself.
Which is the second thing. Oak is the most famous Pokemon researcher in the region, second being Fuji possibly. It's common knowledge that famous people will also be famously known. She even lives in the same town as him, with a population of roughly 9 people in the town, she has to have bumped into him at some point.
Regardless, this is not a bad theory.
Psychics WERE broken in gen 1 and this is proof. :)