Hey, so..... I'm pretty sure that by a combination of gemetics and Rose's particular interest, amethyst is the closest thing Rose/PD has to a daughter. For me that seriously corresponds with how amethyst has been acting like the older sibling who got out of a toxic household and is trying to support her brother who's still in it when it came to finding out about Rose/PD. She's the only gem who just wants to know how Steven feels and prioritizes his emotional state, rather than making it about her (not that Pearl and Garnet didn't have good reasons).

Amethyst and Steven are so close that they don't even need to dance to fuse. There has never been a intergem fusion on the show that didn't involve dancing. Not even stevonnie. I feel like theirs is the unconditional love of siblings, the only people who can understand fully how the other feels.

Amethyst is the only gem that doesn't initially condescend or doubt Steven's intuitions, despite the fact that Steven regularly surprises even Garnet and is regularly underestimated by Pearl. She supports him when he questions things, even when she can't provide an answer.

Amethyst's relationship with Steven often gets overlooked because she's the least motherly, but I'm pretty sure that's why they have such a strong bond. She gets him, and doesn't treat him like a helpless child. She's been in his shoes. She's always gonna have his back.

She's his sister.