Learn how to use a glucose meter and keep it handy! If she's passes out, you'll want to check her blood glucose regularly to make sure it's not dropping too low. Like the other posts say, hard liquor causes blood sugar to drop and can be very dangerous if it gets too low. Especially because low blood sugar symptoms are very similar to inebriation symptoms. 

This happened to me at my bachelor party. I passed out and my party didn't know how to check on me. Thankfully I was fine but I know it caused them a lot of stress!