How can I be a better Libero to my team?

I've been playing volleyball for 7 years and I absolutely love it. I have never played on a club team (I want to, I just can't afford it). I believe my two strongest points are my serving and my digging. Last year was the first time I was actually put into a game as a Libero and I continue to serve as my high school's Libero. Unfortunately, we got a new coach (and she's not very good) and I don't think she's putting me in when I need to be in. I don't know whether she thinks my skills are shabby.. Or what. I prefer to be a very aggressive player. I'm not afraid to run into people or dive on the floor- anything to get a ball in the air to my setter. I'm very loud and competitive on my team. How can I prove my skills to my team and most importantly my coach so I can get more playing time? Also, if you have any exercises for improving vertical jump would be appreciated. I'm only 5 feet and I cannot play the front row unless I improve my vertical leap. Thanks!