Is it dangerous for my 5-month-old to sleep with her blanket over her face?
It is extremely unlikely that she could suffocate with this light blanket over her face while lying on her back. She is old enough to clear her nose area if needed. That said, I'd give myself a little extra reassurance by some judicious pruning of that blanket. I'd begin by cutting it in half and in a week or so later, in half again. Not only will this reduce the face cover but it will also allow you to wash that "lovey" and will provide spares if one or more is lost. Most children like the feel, smell, or sight of these precious objects, so the more you have put away, the less likely the catastrophe of permanent loss. The small pieces will let you and your pillow-covered husband sleep more soundly, too.