You’ve received some very good suggestions so far.
Do you have to use a track? My thought would be that perhaps you can find a good walking path in a nice park or forest, paved but with plenty of greenery and fresh air. Especially if there is one with little hills and valleys. Since she is living with depression, this venue might be more refreshing than a track. Just a thought, since you’re meeting her outside anyway… You could alternate between walking and band work.