After A Good Bath, Why Does My Lab Puppy Stink After She's Been Outside?

Because you need to dry her hair before going out. Also can be that as it's not dry enough, she sweats too much.

Quite likely she is finding something to roll in, possibly her on feces.  You need to clean them up and anything else she might find.  

Also if she stinks before going out, she may have an ear infection and need to see the vet.  

If you don't let them roll in stuff, dogs don't need baths.  Feed a decent chow and as little else as possible, seldom if ever bathe the dog, and brush it daily with a soft bristled brush.  I go years at a time without bathing my dogs.  

By the way, dogs really don't sweat.