Sharing profits before going to work

On holidays, I don't want to work with the 17-year-old brat from the back of the house, so the supervisor always makes me, the only one from the back, work as front staff. But I applied for a back-of-house position because I didn't want to work front-of-house 🥲 That brat seems like they're here to replace me _(:з」∠)_ It's not age discrimination, they're genuinely a brat. They have tattoos, spend money as soon as they get it, constantly curse, brag, love to eat, and are picky. Tattoos are fine, but last month they got one on their leg too. They always change into front-of-house clothes in the back and keep asking if I mind, like who wants to see that? =_= Money talk: They talked about buying an iPhone for ages, then after buying it, they had financial difficulties and wanted to resell it. No need to explain the cursing, there's too much of that. Bragging: Said they won a few thousand on a receipt, a few thousand last time too. The day before yesterday, they posted a video in the work group chat saying they won 75,000 and would treat everyone working yesterday to drinks. Winning that much and treating people to drinks probably cost less than 500, so maybe it's better not to mention it. They didn't treat me when I wasn't there, so I have the right to lecture (x) Eating: We have desserts at the restaurant. They'll snatch uneaten ones from customers, and even expired desserts from other places. But when it comes to vegetables, they say they can't eat them. Yet, they're the first in line for sweets. They also love to find fault with others and report them. Then they turn around and say I'm the one who reports people, which is absurd. Unless it's a really serious situation, I don't report anything. I only answer when I'm unsure or when the supervisor asks, but I'm too lazy to elaborate. They just keep saying they don't want to work with me. The pressure of the speed required for back-of-house work is already significant. The white hair on half my head is becoming more noticeable, and it shows when I tie my hair up. Now I have to deal with customers face-to-face too Q_Q