Confused *spoilers*

It seemed to me at the end , Shae was mentally ill and lulu was all in her head but when they go to the guys apartment to ge the address of the rapiest , he acts like there is 2 girls there and I think says "what do yous want" which makes me think maybe she wasn't imagined , but then at the diner scene , when the car is driving away there is a shot of Shae sitting there alone , a bit confusing