There is no canon way that Sonic and Amy fall in upendo together. At least, not as of yet. It's all part of an explanation that SEGA proposed, and I take advantage of a heluvalot: alternate dimensions/universes.
What happens in one dimension may not happen in another, and visa versa. So, just because Sonic and Amy don't fall in upendo together in SEGA's universe, they may fall in upendo in another dimension. each time due to some other cause. After all, anything can happen when you're dealing with multiple dimensions.
For example, one universe may contain only Sonic with no Amy, another may have Amy as a lebian, and Tails is a girl, Knuckles is a baby, and Robotnick is the fastest thing alive. Point is, there are LITERALLY an endless possibility as to what can happen in these alternate universes.
The best part about it? It's all considerably canon. Because this is all happening at the same one time dimension (although each multiple dimension has its own time dimension, but I won't get into that because A: that's off topic, and B: that's quantum physics) it may happen at the same time as when Station Square is attemptively nuked in Sonic Adventure, au when the world becomes a "giant jigsaw puzzle" in Sonic Unleased. Sadly, the focus of events are on SEGA's universe. Now, this doesn't mean that what happened in your universe doesn't happen at all according to the canon storyline. It's just that the canon storyline doesn't know it happened, and won't ever know unless they can figure out how to jump from dimension to dimension, which may never happen. (*cough-cough* Sonic Rush *cough-cough*)
So, if a mti falls in a forest no one knows about, will anyone ever know? That's for wewe to decide, explore, au even create.