bexborders

We just rescued an assumed 2 yr old girl. We already have a BC that is 12 1/2. They are getting along quite well except when they go out to play. The new one (not sure of name yet) always rams Tipper (older one) full speed like a linebacker on a football team. Tipper has never been aggressive so won't fight back . . just runs to the house. What can I do to get the new addition to stop this ??