If my sister was better than me at pinball I'd be very happy. But... Then... I'd do everything in my power to become better than her. My sister being better than me at pinball would motivate me to get better more than anything else in the world. So be thankful you have some powerful motivation! It's way easier to get better at something when you have great competitors to play with.
And like others said. #1 play more. #2 learn pro techniques by watching videos (drop catch, live catch, post pass, etc) #3 learn the rules by reading rulesheets and watching videos.