Aquamarine is a Homeworld Gem apart of the Diamond Royal Court, specifically Blue Diamond's court.
Physical Appearance
Aquamarine is a small Gem, only about half of Steven's height. She has a cherubic appearance and a bright cyan-blue complexion, navy blue eyes, no nose, and chin-length, cerulean-blue hair worn in a bobbed style. Her clothing vaguely resembles a prep school uniform, consisting of a blue vest worn over a dark blue dress with a white collar, white wrist-length gloves, white knee-high socks, dark blue flat shoes, and a dark blue hair bow that she can turn into her wand. The intersection of her vest and the lapels of her collar form a Blue Diamond symbol, hinting towards her superior. Her teardrop-shaped gemstone is located beneath her left eye, and her water wings are similar to a butterfly's wings. Her outfit, wings and the use of her stasis wand give her the appearance of a fairy or pixie.
Personality
Aquamarine, despite her childlike appearance and demenour, has an arrogant streak, frequently believing that she is better than everyone else, pointing out how important she is on multiple ocassions. She thinks very highly of herself, similar to an ego-filled celeberty to a crowd of admirers, as she wondered in a egotistical way when the lesser gems will give her some privacy when she first saw Jade. Still, she does show some temperament as shown within the same conversation.
Like many other Homeworld Gems, she answers to the Diamonds first, although she will openly admit to one's faults if they're not present, evident when she was talking about Pink Diamond. This is probably due to her egotistical nature, though she will still follow orders to any Diamond, especially if it'll give her an upper advantage in a situation.
History
Season 6
Aquamarine appeared first after a meeting with Blue Diamond, coming out with Topaz to find Jade waiting for them. She paid her little mind at first, especially when bringing up the Gem War (which she cared little about), but she did eventually complied to her, saying to make it quick. When asked about Pink Diamond, she at first questioned it to The Trial, but eventually told her of her Gem War involvement. She then placed her aside, saying they were even as she got her info and Aquamarine got her admiration, before going on her way.
She doesn't appear again until the finale, shown that she had been found by White Diamond and apprehended for talking of Pink Diamond to a Crystal Gem. Upon released, Aquamarine demanded an explanation, though it only took the promise of her being dropped of charges to have her apprehend everyone else, much to their shock and anger. This promise didn't last too long though, as after bringing them to the throne room, was removed of her wand, but still was left out of hybridizing unlike the other gems.
Season 7
After many of them escaped, Aquamarine was left behind within the White Diamond Space Station, barely able to keep alive with all the Corrupted Gems and Cluster Gems abroad and let loose. She was eventually saved from the station alongside Pearl after half of the Crystal Gems arrived in the station to rescue them. While rescued, this left her and Topaz stranded on Earth, spending much of the season trying to get back to Homeworld.
It's assumed she returned to Homeworld shortly after the Gem Wedding, being one of those present for it.
Season 8
Her more prominent role was during the Festival Arc, being the gem apart of an "arranged marriage" with Emerald, and spending much of the time with Emerald and trying to stop it. It is revealed though that this was all a setup in order to teach her and Emerald about respect to others.
My Little Universe II
She shows as one of the allies for the Harmony Gems during the final battle with Grogar's Army.
Abilities
Flight
Like Lapis Lazuli, Aquamarine is capable of flight, and is often seen doing such with her butterfly-shaped wings.