On the subject of working under Remiry, is Sakuya lucky?
The odds of her being scrapped are close to none.
Remilia has far too much use for her, but the same can't be said for anyone else currently. Thinking on it a bit more, it's quite sad being more than disposable, but you're there to serve here every order, even death. For all you know, with her control over fate, you may as well have a slight change of not having an unconventional ending for yourself if sh feels generous in doing so.
Fairies are odd. They don't know how easy they have it. Even if they're easily overpowered by everyone else, it doesn't matter. Just look at Clownpiece and what Junko did to her, or even Cirno's determination!
But hey, what can i say. Most in Gensokyo won't even acknowledge that you even exist if you have no use to them in the first place. Well, you could be viewed as free food if you're human.