A little of background: my fiancé is dealing with depression. She had a very hard time when she was mostly laying in bed, crying and being anxious. Now, thanks to medicine she's taking, psychotherapy, changes in our life routine and our (relatives' and friends') assistance, she's getting well. Most of the time she has energy, mood, and plans, though she needs to be careful not to get too tired and not to forget about medicine.
During this lying-in-bed-and-crying period, she wasn't moving a lot, not to say about going outside. As a result, she gained some weight. Now, given that she is getting better, she wants to make her body the way she likes it. So we've started some sports together (bouldering, running, and athletics). We go easy on that, we've got plenty of time and we're trying to have joy. We both know that after some weeks of regular suffering, sport starts to give you joy and you become dependent on it (we both have sports background). But now, we need to go through the unpleasant part, when the body tries to stop you from exercising.
We do not track our activity and weight loss as it is suggested in comments. I think it's a good idea and we'll try it.
So, my fiancé explicitly asked me to help motivate her. E.g. when she tells me she exercised today, or when we together go bouldering or running, she would've felt more motivated if I'd make something for her or I don't know what. I'm trying to notice every good moment and even her trials and I always compliment her on this, but I feel that's not enough.
So, the question is: how to motivate or reward a person on exercising?
I need something that can be done quick, best of all immediately and many times. If it can be done over the phone/internet (when we both are in our workplace) it would be perfect. Please remember she has depression: that means she can out of sudden get tired, lie on the floor and start crying. That's because she hasn't gained enough power yet. I do realise that rewarding too many times can be diminising the value of reward, so it's better if I could vary different types of reward or motivation.