That sounds about right. What I am worry about is what will happen if Fluttershy and Spike realized that someday he will grow up. Will she be afraid of him? Would they stop being friends?
She might be scared when she realizes initially. But... I can't help thinking that if she watches him grow up slowly, it won't be the same kind of fear as for a Suddenly Adult dragon? Like - she knows who he is. She will've been there for every birthday along the way. Listened as his voice changes. Even if she feels a shiver sometimes looking at a Wall of Purple Scales, I don't know if she can go from seeing Spike to seeing him as Not-Spike-Actually-Scary-Dragon. But I guess part of that depends on the nature of the fear. If it's like a full-on phobia... I don't know how they'll deal.