I too had the same concern re: Sammi interacting with a large dog, since my sister has a pitbull mix...I must say Sammi interact more with him than my moms maltese who is her size
Storm (the pit-mix) lets Sammi jump on his back and ride him around like a horse! It is the funniest thing to see! Storm is 11 months old and 70 lbs

Sammi is almost a year old and 9.5 lbs! Go figure she would prefer him over the Maltese