How do you deal with trollers?

I had a recent ranked game and there was an irelia that kept trying to flank the enemy team 1v5 and would get chased down. I told her that if we grouped, we had a stronger teamfight comp because we had wukong and zyra and draven ulti. I said I was trying to give her advice but she said she didnt need it and she kept getting chased down by rammus, she did this almost 5-6 times and the game ended as all of us getting picked off one by one.