Thanks everyone, for your kind words! Sammie does get to see Bernie quite a bit. Bernie lives with my parents, who are retired. When my husband and I go to work or on extended errands, Sammie goes to "Grandma and Grandpa's" house to hang out with Bernie. Based on the responses I've gotten so far, I think the next thing to try is more socialization which = more trips to the doggie park.
Or does anyone happen to live in Seattle, who wouldn't mind setting up a doggie play date? I would love to rescue another little one but I'm in a rental situation where the management company has already bent their 2 pet maximum rule for my husband and I.