When I first started playing at my husbands encouragement, I was placed in Khelonaar... he was in Arendyll. Since we play on computer, I had the option to start another city in Arendyll so I could be in the same Fellowhip. I now have 10 cities and 2 accounts (I had been using my second account in Arendyll as a teaching tool for our newbie players since we started out as a training Fellowship; an example of what you
could do with your city at each level as I - and hopefully, they - progressed through the game. Now that everyone's progressed into guest races, it's not quite as important for teaching.
) The short answer to the question of whether the two of you can play and be in the same Fellowship is - yes, if she's able to start a new city in the same world that you play in. I can't give any advice if you're playing on mobile app though...