I know what the problem is, Sadie finds your daughter irresistible and bites her the whole time, your daughter can't not react (because she's 5 and kids can't help but react to pain) and so you're in a vicious circle because there is no way currently you can train Sadie not to bite her because Sadie gets so much fun from it!
Right?
I have this t-shirt.. several times over. I was given some great advice by a dog trainer and she was dead right. Keep them separate, a lot, until the pup is older and has learnt bite inhibition on you and has also finished teething....
There is no way you can stop what's happening between them at the moment but your pup will grow out of it and the more you can avoid the nibbling sessions the less they'll happen as the pup grows up. Let the pup play with your daughter on a long line while you supervise.. the minute the pup starts biting her, without any confrontation, remove the pup to a 'quiet' area (I used a baby gate across the kitchen and the pup had his crate/toys in there etc and kid stayed the other side). It can take months but it pays off, I promise. You also avoid your child becoming too nervous around the pup and the pup gradually learns that to stay and play, she has to play in a certain way which includes not biting
Children (even the calmest child) over stimulate puppies and excite them so they are no good at helping to teach a pup what's acceptable. However, if you manage them both and avoid any really bad incidents (child reacting to the pain and hurting the pup for example) once the pup has grown up and is a happy adult dog that's never had a bad experience with your child, they will be the best of chums I promise
Hang in there you have a long road ahead but you will look back on this time and know it was worth it when Sadie is your firm family friend