Well... It did come off a tad bit sarcastic, but it was certainly very good of you to follow up with an apology comment.

So rather than being mildly put off by your first comment, I'm now left with the impression that you are probably a very good person!

But ya, 13 miles, despite the exoskeleton robotic legs is still an exhausting feat for someone with her level of paralysis.

It involves usage of arm muscles, and many more other muscles throughout her body (than one might suspect), in order to maintain upright posture/position/balancing.

I suspect it's probably a bit like like a human travelling from Earth-gravity, to another alien planet, with higher gravity than Earth.

Once on that higher gravity planet, your heart, muscles, endurance/energy levels would not be accustomed to maintaining upright posture for prolonged periods, at first.

SO... in short:

because of her paralysis, which limits the level of work outs she can do (and she's probably usually confined to a wheel chair or bed) she's starting from a much lower baseline of endurance than you and I...

just like that human that travels to a higher gravity planet.