In the movie Batman vs Superman, at the end of the first nightmare we see him have, Bruce Wayne wakes up in his bed and there is a girl sleeping besides him. There was no reference to her before or after that scene. I thought the only people that stay in the house are Bruce Wayne and Alfred. Who is this girl/lady Bruce Wayne slept with?
Though the movies often neglect this Bruce Wayne maintains an image of a millionaire playboy to avoid suspicion. It's a common thing for Bruce to have girls around to keep the gossip going.
Not sure why she was in his bed though as in the comics Bruce only pretends to sleep around and drink.
Though it's worth mentioning that in the film he does drink for real so it's reasonable to assume that he sleeps around for real.
So to answer your question, no one important. She's just there to maintain the illusion.