By your own logic, isn't 'famous journalist' & 'world traveler' similar levels of information in order to "fill in the rest"
With the background of her athletic/outdoor interests & how she was raised + those two details, it's not hard to imagine she was traveling the world, was given an opportunity to try bull-riding, somehow was very good, briefly lived out some fun, glory.
or alternatively, she went on an assignment to cover an aspect of bull-riding, or under-cover in a way she took on that role to learn more, etc.
If the leaps necessary are.. Marshall = SCOTUS = Climate change, or something of that ilk, can't we do the same for Robin?