This is the most heartbreaking advice to give your poor, fragile, bone popping Vata friend but it works.
If you haven't slept well, sleeping in past sunrise is like going way past your appetite signal, getting into severe exhaustion from hunger, and eating way more than you usually do because your desire is bigger than your stomach fire. Your body will react by bloating and indigestion.
If you get to sleep desperation, sleeping in is also a heavy meal. If your nervous state is fragile, then adding that extra weight will make you feel worse in the day. You are just better getting up and getting through the day - you will be tired but you won't be carrying the extra weight on your wee little asymmetrical back to make you feel wretched.
This approach usually takes one day to recover your rhythm. If you sleep in, it could take days because of the rhythm upset.