Sounds like Sammy is just a little bit miffed. If Sammy and Happy can be playfull together, with you, you might want to start there. Just go slow and don't be pushy. You need to find a common ground for the 3 of you, that will be enjoyable and rewarding. Also, show Sammy 1 on 1 personal attention to reassure her she is "still" your #1, but do this out of view from the new dog.