I had an interesting conversation with someone who pointed that really, these two have had almost no interaction with each other.



However I do think they could work given there personalities. Sweetie Belle seems to be the most sarcastic, cautious, and naive of the group. Which is very similar to Spike. She also likes girl things like Rarity but is up for doing doing boyish things. Which is similar to Spike but in reverse. There is also the obvious fact that Spike's crush on Rarity means he would likely find Sweetie Belle physically attractive when she is older.