Why is Evelyn Sharma kept away from YJHD

If the buzz is to be believed Evelyn Sharma plays the girlfriend of Ranbir Kapoor in Yeh Jawaani Hai Diwaani. If the reports are true, wonder why is there no mention of her in the film's publicity. Is her appearance, intended to be a surprise or the makers don't want the jinx of Evelyn Sharma (all her Hindi films have flopped) to hamper the box-office prospects of Yeh Jawaani Hai Diwaani.