I have a really dopey, soft older dog and a loopy, bitey puppy at the moment. My pup is a lot smaller than my older boy, but likes to take flying leaps at him and nip wherever he makes contact.
The first few days he just stood there looking at us with a panicked look on his face if the pup started charging around biting and nipping at him, so we used distraction and reward to redirect the pup's attention onto a more appropriate activity.
A couple of days ago, we noticed him start to curl his lip a little when pup got too much. Then finally, the other day, pup ran up to Lurcherboy, ran underneath his stomach and nipped him somewhere exceptionally painful. 
That time Lurcherboy really told him off. He growled and snapped at him, but without making contact and pup squealed like a little piggy and shot off with his tail between his legs.
Poor old Lurcherboy was really upset and worried we would tell him off, but we stayed completely out of it and since then he has put pup in his place a few times.
I agree with others upthread. You need to take control and remove or distract pup until the time comes your older girl has gained enough confidence to tell her off herself.
In the meantime, make sure your old girl has somewhere safe to retreat to. Nothing wrong with her taking herself off upstairs if that's where she feels safe. Don't leave them alone together and make sure you are giving your older dog plenty of 1:1 time as well as the pup.
Your pup is very young and only just out of the rough and tumble of her littermates, it will improve, but you need to be the one in control of their interactions in the meantime.