I am not a Barbie expert, but I did own the blue dress as a child.
I thought it was part of a fashion pack, only because I don't remember a doll being attached to it, but I looked up "My first Ballerina-1987" and things that I thought were included in the fashion pack, are actually included with her. So I am NO help at all.
I'm sure the blue dress came out along the same time as "My first Ballerina-1987" though:)
Does your dress still have the sticker that was centered on the front of the top of the dress? I remember a sticker of some sort being there, but I can't remember what it was
Maybe that could help identifing it. I remember loving that dress as child<3 I probably still have it. It looks so nice a doll.