I think Nikki secretly knows her attitude in the house is going down well with the audience, otherwise she would've been evicted by now. So the way she is in the house I reckon is almost definitely an exaggeration of what she's like normally. As a whole she's loveable though - annoying at times, yes - and it would certainly be difficult to live with her. But watching her on BB is so much fun and I think deep down she knows that! Go Nikki!
