The animals match the hair colors. As for the personalities, I don't think it was meant to be analyzed that deeply. One could just call Yuri more of the cute/cuddly type and Sungah the pretty foxy type. Like I said Yuri even has a "bunny ear" headdress as part of her character design, it probably isn't any more than that.
No matter, at least we agree they do represent the four girls.
Its sort of a red flag for me when she wonders aloud if he would throw her away. It not only comes with that clingy feeling but also implies she somehow already think they're a thing or at least good friends.