I am fuming about this girl on facebook i need help now ? :'(?

[YaDunkno 2K11]

Hi people i have a very sad story so please listen and tell me what i should do.
Two days ago i added this beautiful girl called Mila on facebook, so now i am waiting for her to accept it. She accepted my friend request yesterday but it wasn't her who accepted it, it was her mum. As i went on Mila's wall all i saw was R.I.P, this girl called Ava had bullied Mila so much she committed suicide. As i was scrolling down Mila's wall i saw a post on her wall from this Ava girl saying and i quote "Mila has committed suicide well that's one less slag around" after i read that i was infuriated and i couldn't understand why someone would write that to someone. About an 1-2 hours later Ava wrote on Mila's wall again but this time saying and i quote "Mila Cook Is gone hope Danielle Lauren Is next both slags" i was now so angry half of me wanted to kill this bitch the other half wanted me to go to the police. I am disgusted a 14 year old could say such things about a 17 year old that in the end she committed suicide. The upcoming generation makes me feel sick. So please people tell me what i should do ? Do i go to the police or what ? (i'm in the UK)