Who was girl behind Kat-Ranbir break-up?

Who was the girl who caused a break-up between Ranbir-Kat, no it is not Deepika. There was someone else other than Deepika Padukone who may be the cause of split between Katrina Kaif and Ranbir Kapoor. No one wants to name this mystery girl but our sources tell us that this girl, who is younger to Katrina was the cause of a rift between the couple. Sources say that Ranbir was getting closer to the girl and Kat was very much miffed with this face. The couple has allegedly split and Ranbir has walked out of the love nest. He has moved to a new flat in Andheri. The couple is tight-lipped about the entire episode, they neither spoke about their split and had also not spoken about their affair.