Prepositions aren't so hard... just keep reading and you'll get used to how they work. For ability or skill, use AT. "I'm bad AT prepositions." You'll often hear "bad in.../good in...", but this is a common and silly mistake. "Tease" needs an object, not a preposition. "They are always teasing ME..." (The sentence can even end here.) "Peter" is extra information, so that does need a preposition. "They are always teasing me ABOUT Peter."

I'm bad AT prepositions. They are always teasing me ABOUT Peter. Maybe you like Peter, or Peter likes you, and your friends laugh AT you or make fun OF you ABOUT this?

lol, we all hated prepositions once. anyway both correct. tease with a lollypop tease to death.