Wanting to show western but...

What I’m saying is a productive way of dealing with the contention must be found. My sister’s problem (at least one of them) was that she was never told no. If she threw a tantrum, she got her way. She wasn’t taught to productively deal with her insecurities, and her go-to reaction to avoid competition became the tantrum, and she’s never gotten out of that mode. You can’t just throw a tantrum and have everyone back off and let you have your way. Life doesn’t work that way. Me? I needed to learn a productive way of advocating for my own desires that offered a win-win. Rather, I got irritated and decided I was so sick of being pushed out of everything else that I was just going to run roughshod over her fears and insecurities. My parents never taught us how to handle sibling rivalry, or how to channel the competitiveness. My sister ended up a spoiled brat, yes, but it’s a repeated pattern of tantrums getting her what she wanted that caused that. It doesn’t excuse me not finding a way to propose a win-win, or my parents for not stepping in to offer a bit of advice.

I think I’ll bring it up to my mom. My dad, maybe too, but he’s not as understanding.

Great!
I hope that bringing it up can help you get somewhere.

all along I’m thinking ‘why can’t I be doing that?’ And the answer is pretty much because my sister doesn’t want me too. Which brings me here. I know it should be my decision but I don’t want to stir things up. That’s what makes it hard.

You’re absolutely in a hard place.
You know the probable outcome of ‘just do it’, and the ruckus that could bring up in your family. So that option seems crappy.
But the other option, to ‘protect your sister’ by not participating, already IS crappy for you.

So hopefully you can find an Option Number Three that isn’t crappy at all.

I was thinking about this last night- maybe your sister want’s your father’s attention. But is there any reason she wouldn’t want yours, too? You could take time to be her Number One Fan/Support Crew while she’s showing, bringing her a favorite snack, giving her boots a last-minute ringside shine, taking video or notes at her lessons. And she might be able to do the same for you.

Just think what the two of you could accomplish, if you weren’t struggling against each other, but fighting FOR each other. You’re already trying to do right by your sister, by not participating in the Western classes because your sister doesn’t want you to. But that isn’t a healthy way to help your sister…nor is just doing it anyway, leaving her to ‘just deal with it’.
So figure out how to do right by your sister, in a way that IS healthy.

How about, if you brought her a sno-cone colored to match her ribbon after her class? Or the ribbon YOU thought she should have won?

How would you feel, if you felt like your sister would reciprocate for YOU? If you thought your sister Had Your Back, rather than feeling upset about you encroaching on Her Thing? If she was there to help you?

How would it be if the ‘win’ photo of Your Awesome Sister was not her, alone on her horse, with a pretty ribbon… but of your sister on the horse, you holding him, your parents there too because you all helped her to make it happen?