It's at least a mile and a half of tunnel between F and T. I actually can't remember how you even walk from F to E. I wouldn't suggest it for anyone who doesn't like to walk. Even with the moving sidewalks, there is a break in the middle of each set between concourses and the full width of every concourse itself. So while you are in a tunnel, you are on a walkway and then a break but when you reach the next concourse, it's walking all the way to the next tunnel. Just get on the train, grab a seat in the back and ride all the way. It's much easier.

I also agree on just getting assistance. They can put her on a "beep beep" as I started calling them as a kid... the airport golf cart things.. and get her most of the way.

Plus, walking from F to T would take a long time. I only walk to my concourse when I'm about to get on a really long flight and want to exercise first. Even using the walkways, it is a good bit of walking.