Why does she feel the need to lie when I am only trying to help her?

A colleague has been complaining about her weight. I offered to help and share our activities using iwatch to count our steps.

On average without exercise, I do 15000 steps. Since I am trying to help her, Ive increased my steps and walk to most places. All up, I'm doing 25000 steps a day. For the last 7 days, she has been stepping the same amount.

This morning, I found out that she has been lending her watch to one of our colleague when he is jogging. I don't understand why she would cheat herself. When I asked her about it, she still lied.

Oh well, enjoy your doughnut and cream, diabetes is knocking,