One of the worst things I've ever done

I've done some fairly bad things in my life, cheated on boyfriends, sneaked out of my house at 16 and just been a general bitch sometimes, but there are only a few instances where I've been truly evil, and this, my friends, is one of those times.
When I was 16 years old, my sister, who is six years older than I, got engaged. This was fine; I was happy for her and had no problem..that is, until she turned into the original Bridezilla. God help me, I love my sister, but she was out of control. Incidentally, she may not be all that thrilled at my telling this story, but I figure the people in my life better toughen up before my memoirs are written.
Anyway, every conversation, every family event was colored with "wedding talk." The caterers, the florist, the harpist, the transgendered videographer (don't ask). Everything in our lives was about this wedding.
Let me say, yes, I was jealous at the attention she was receiving, but because I'm the youngest, I was always afforded a certain amount of doting, which was lacking while the wedding of the century was planned.
I can be quite petty, I'm not proud of that, plus I was a teenager, for God's sake. There's a line in my favorite book: "Teenagers, by definition, are not fit for society." So very true.
Alright, so during this time, she was living at home planning the nuptials, and she and I had some, shall we say, friction.
The culmination of this was arguing over the shower in the morning. Either I was shafted with absolutely no hot water, or I had 15 minutes to make myself look good, which, in high school terms, is not nearly enough time. My only saving grace was going through the "grunge period," which I actually cheated on, because I refused to go out without make-up. Had I been an actual Nirvana groupie, I could've compromised, but I was in Macon, MS for God's sake. There was only so far I was willing to go with the look du jour.
Anyway, we argued constantly, finally having this exchange. She said, "Emily, I know you're jealous, but this is my time. You really should just accept that and understand that this is all about me and get over it."
That was a BIG mistake.
I went into the bathroom, fuming, and began to compile a list of things I could do to her to exact my revenge.
What I came up with was really quite something, and this is the part that curdles some people's blood.
I grabbed her favorite shampoo, positioned it over the toilet and urinated an amount I deemed sufficient enough to taint it; I took her toothbrush and ran it inside the toilet bowl, and I put super glue in her mascara tube.
A number of things happened. A few days later, she stopped using aforementioned shampoo, complaining that it didn't seem to clean her hair, a few weeks later, a guy that I was seeing at the time used the shampoo because I forgot to tell him not to, and I had to handwash his hair while enduring his ruminations about what a terrible person I was, and finally, she didn't find out about my actions until three years later when another ex-boyfriend mentioned the incident, thinking she already knew.
She didn't speak to me for half a day, and I honestly don't blame her.
So, I wrote this for two reasons. One, to share this shameful story with others, and two, to publicly apologize to my sister.
I'm glad we don't have that kind of relationship anymore, and I love you. I'm sorry I was a huge brat when we were growing up.