Should i beat her senseless?

ok my old best friend from a while bac n me were chillin n i told her sumthin i knew about one of her friends bf's cheating on her, the only thing i asked was for her not to say my name. she told on me then when i yelled at her she got mad. thinkin shes in the rite for screwing me over. now shes sendin me threatining e mails n shyt n her friend thinks i lied about the boyfriend whos a cheater. shes also makin fun of me n stuff now n i tryed to tell her since she told on me to ppl i would do the same cuz she tks about all her so called friends..... i swear she only thinks about herself. now shes got all her friends against me n i just donno what to do.. if everyone wants to fight me then i will but i dont wanna get into anymore trouble ......HELP i donno what to do