As One Pleases
One's Own Convenience, One's Own Way, One's Way
noun, な adjective
The hand (or person, as you know 手 often refers to a person) that wins gets to do as one pleases without regard for anyone else.
かって
The reading for this is weird. It's all kun'yomi, which luckily you've seen before, but still strange. I guess when you do as one pleases you can read kanji however you want, in this case the kun'yomi readings. Do note that there's a small っ in there before, presumably to connect the two readings of the two kanji together.
ほんと、勝手だよね！
You are so selfish!
勝手なことばっかり言わないでよ！
Don't say whatever you want.
「サーモン！フグは五回も浮気したんだよ。そんな男のこと、信じちゃダメだってば。」「分かってるんだけど、でも、彼、私がいないと生きていけないって言うの。」「じゃあ、もう、勝手にすれば！」
"Salmon! Fugu cheated on you five times. Never trust a guy like that." "I know… but he says he can’t live without me." "Well, suit yourself then!"