My friend who is a good runner already finished her run.
How do you feel about your friend finishing her run before you?
I'm bad at running and I'm jealous of her good results.
I understand how you feel, but comparing yourself to a good runner like your friend isn't very helpful. Feeling jealous of your friend for being a good runner isn't going to make you run faster.
How do I improve then?
You practice running as much as you can.