The effect of not getting enough sleep the night before is around 40% in cognitive performance drop (thinking ability) the next day. If you have work the day after her night out, you will be miserable for longer than she spent getting her jollies. That's an asymmetry of cost and reward you might want to consider. And she should, if she is at all considerate. e: That is, the hidden (time + stress) cost *for you* is far greater (16 hours - the whole waking hours of the next day) than just the apparent extra 1 hour it would take to do her the favour of picking her up.