I can't understand why she's bothering you....whatever she does at the gym is her own business...you can't rule others...you can't tell them what to do or who to talk or what to wear!!!!
C'mon....this is really bad....you got to move on and don't pay attention to that lady....people are everywhere...people that we like or we don't like...we have chemistry with or we don't....but they are people....
I want you to next time that you see her think this way that she got to have lots of problems of her own...family issues, work related problems, money issues, love problems....she might be so frigile at the same time like any of us....and she might need a lot of help and support like any of us....forget about her attitude think about her as a person who has a life with probably lots of suffering even like all of us....
hope this helps....
people who gives us hard time in our life will make us to be a better person!