Been re-reading the Reflection comics recently, which give me a thought.

Would the EvilCelestia find EvilSombra attractive like how the GoodCelestia find GoodSombra attractive?

Or would that also be reversed/mirrored, and she be repulsed by him?

Evil attracks evil. Therefore is stands to reason attractive evil delights other qttractive evil. So, yes.

Evil attracts evil. But I don't feel like that phrase fits with those two. Their ambitions are too similar that they would likely clash rather than work together.

Unless you are referring to Casino/Eris' Daybreaker instead of Starlight Glimmer's Daybreaker. I can see something working out. This would eventually lead up to Daybreaker being the head of the pair.