Amy was jealous. She was always jealous. But she realized this was a different kind of jealousy. Amy was jealous of Sonic about Sally. Usually it was the other way she would be jealous of Sally about Sonic. This was number 1: weird and number 2: off. Amy didn't know why, it's like something switched in her brain. Suddenly she realized how beautiful Sally was.
Now she was confused. Really confused. Especially to herself. Amy has no idea why she's thinking like this. But now she has an idea and an insane idea but an idea nonetheless. Amy begins chasing Sally like she once did Sonic. Surprisingly enough, Sally seems to like it. Taking it in stride and not minding the hedgehog latching onto her. Amy keeps doing it, not only liking Sally but because she likes the attention. Soon enough all feelings of Sonic go away, replaced by new feelings for Sally.
Sally doesn't seem to mind at all, surprisingly. Even giving Amy back some affection. In turn Amy gives back even more affection. Which ends up creating a loop with more and more affection between the two. Yet slowly so nobody questions the two being so close. Eventually Sally developed feelings for Amy. The two became even closer. So close that one night when they were cuddled up together. Sally kissed Amy, to the others' shock. Sally almost backed away and ran but then Amy tackled her and smothered her. Confirming her feelings towards the other. They went back to cuddling right after.