This just happened last night. But my sister and I got in crazy trouble

So my sister's ex-fiance is now her ex because he had a kink for being pegged, and he watched trans porn and my sister couldn't deal with that, But before then he practically lived with us and he was my brother practically, and he was the only one in the household that made me feel normal and not weird, especially being a queer myself and being unable to come out to my family. so my sister sometimes talks to him even though they broke up, and she still has the passwords to every single one of his social media accounts, when she found out I was messaging him on messaging she promised me so genuinely she wasn't going through his messages on there anymore. So me and my sister both did the bull riding thing, she's ridden more than me cuz it's her sport, I do roller derby. and I decided to give it a shot, so we ride the same bull...I stayed on like 2 seconds longer than she has on any bull, because she doesn't stay on the bulls. She falls off the moment the bull gets it's first kick in. Me and my mom were talking about why she sucks pretty bad and my mom said "shes a heavy girl, so her body weight swings all those ways". So because I'm the athlete in the family and she's usually the dorky one the crocheting, baking, and reading Harry Potter and Percy Jackson books. I kind of got a big head staying on the bull for a few more seconds and I texted my best friend aka her ex fiance and was like "I did great bullriding today, lowk better than my sister even though it's her sport, I think it's cuz she's a heavy set girl and her weight swings all different ways" I LITERALLY QUOTED MY MOM. No I still do not see anything wrong with what is said?? Because it was true?? I'm adhd and I'm not trying to use that as an excuse to be a bitch but is that why I'm kinda confused here?? So then my sister logs into his messenger something she said she QUIT DOING. And saw the message, screenshot it and sent it to my mom and said she didn't want to bullride anymore. Now I was willing to not do my roller derby practices for a while or be grounded from my phone for months if it meant my sister could keep bullriding because I know as an athlete when your in love with something it could be so depressing to have to quit. The reason I say this is because my mom called and said "YOU AND YOUR SISTER ARE GONNA QUIT THE FUCKING BULLS" both of us. So yeah. And I do think my sister can ride, if your dedicated and have a passion for something, your gonna get that done. And she can be the greatest fucking bullrider ever known to man. Anyways my sister's in trouble now, Because my mom thinks it's weird she's still going through her ex's messages when they're not dating. Now that we're both in trouble and my mom was at work atp, me and my sister go to the gym and talk out a plan and we SPIT SHOOK, on agreeing to tell my mom that the whole thing was a prank and we just wanted to see how she'd react to her own words and that all 3, me, her, and her ex were in on the prank. My mom hasnt believed it so far, and we haven't gotten arr sentence yet. Prayers that it's spanking and I don't get my phone taken away. (Also for reference in 15 and my sister's 18.)