What can i do about this nagging feeling i have?

When i was in high school i dated a lot of guys. Being naive i really thought these guys liked me but after a while of dating i realized that they just wanted me for one thing. I really liked thier company but one day out of the norm i meet a guy and he treated me so good i thought finally i found someone whom i can relate to. We dated a few times and then my hormones took over and i experencied my first time at , i was not sure at the time that i wanted it but again my hormones took over my sense. Well little did i know that this guy also knew my cousin and he told her everything that happened and so what did she do run to my parents like a messenger from hell and spilled it all. I thought she was out of line and was accusing me of being a slut which i was not. But every since then she has been making me feel dirty and cheap . Years went by and i did not talk to her , even see her , anywhere and that was working out well for me , i even got married in a church and had two wonderful kids , Soon after this she reappears in my family's life and she still somewhat makes me feel cheap and useless. Now i know that i was wrong when i had the the one night but it never happened again not until i got married to a different guy but hey i was married and she just gave me her stare like she always has and it really makes me mad and i feel the need to defend myself to her. How can i get over this nagging , useless feeling when i am around her , which is not often and not for very long lengths of time? I know we on occasions are going to bump into each other and i want to get some peace from this feeling. I really am glad that the first time around i did not get pregnant but i did not and made sure i would not and that is what she did not and does not need to know in my opionon but she s into peoples lifes that way and i just her to know that no one is perfect and that now i am still married to the same guy after 20 years so she could and should just shut it right?