Don't try the submissive positions, it's not working and it'll probably won't work in the long run. You need to set some rules for the pup. It's good that you're stepping in, now you need to redirect the puppy. She probably needs more physical and mental exercise, and is just trying to drain that extra energy on your older dog. Try walking her more, playing more games, and do some training. Make her work for her food. Try training her "off", so that she gets off of your other dog on command. You can also try the removal technique, when the puppy is getting to excited and rough, you remove her from the room into a quiet and boring place until she calms down. When she's calm, she can return into the room. However, if she acts up again, out of the room she goes. It's kinda like a time out, but the goal is to get her to calm down and not punish her. You don't want to be angry when you do this, just be really boring but firm. Does the puppy respect you? You won't be able to intervene unless she respects you first.