If I had to choose between arenas and trails, I would choose trails any day. Maybe Gidget is the same way.
And look at it this way, trails are the real world, so if she's good at that, that's what counts.
How about working on your arena "stuff" out on the trails (or pasture)?
I don't have access to an arena, so all my riding I do out on the trails, including teaching them to sidepass, back, canter, etc.
Just an idea.