Sleeping with my baby on your chest..

My husband's younger sister has this thing about cuddling her baby nieces and nephews and falling asleep on a couch/ chair. Its her "thing" she passes completely out with them on her chest. She doesn't have kids yet so might not know the risks involved.. we are due with our first baby shortly and I need a polite way to ask her to be fully awake while holding my baby. I am not well liked by my in-laws so it's causing me some anxiety.

I know she means no harm, it's just not safe. And it's our baby, not hers. So we do get to make the rules here. I just don't want to come off as a controlling mama bear or be judged any more than I already am.. my husband doesn't want to say anything even though it really bothers him.

Edit: I can't avoid it, she does it at family gatherings. When she holds a baby she tries to make it go to sleep for the sole purpose of sleeping with baby, room full of people or not.