How can I wake her up?

Julia

So because my daughter Melody was born 3 weeks early, her doctor has requested we feed her every 3 hours which I’m fine with but Melody just sleeps sooo hard sometimes, and I need some tips on how to wake her up. She usually does whenever we change her diaper but right now she’s not dirty. We’ve also tried undressing her and wiping her down with something cool but nope, she doesn’t care today. Here’s a picture because she’s just so cute! 😍