That's just it though, there is no canon explanation for the background of any of these characters.
The only ones with a fell canon background are the Mane 6 and Spike.
So the only background for them is the fanon one.
True, and actually, that's a very interesting point.
Is interesting because the characters that receive background are characters which justification and role is determined to fulfil an specific task in the story, in the case of Gilda, the story is driven to be an antagonist for a main character, and considering their target audience, the dilemma produced by the motivations behind Gilda will result in a complex ethic dilemma, and not a simple one to be handed to the target audience.
All characters have motivations, everyone have motivations for their actions, but this is based on the the background offered, and its a common result that people who follow a background will result engaged with the characters, because often these characters will follow a common sense of actions, which creates some sort of identification with them.
Probably that's the base for a good story, however common sense and individual perception of a situation that does not involves a dilemma will result in an actually identification with characters, I said this previously, but I'm derping a lot today.
And, that actually got me thinking for a sec.
Almost forgot, characters are determinate by their actions, not a strong point for Gilda, but still relevant for the whole characterization and identification issue.
