As the Queen's bodyguard, there was no way for Annabelle to avoid the ball--even if she thought that it was a fucking terrible idea and a great way for some of her power to get out of control, potentially. It put her on display in a way that made her uncomfortable, and she did her best not to fiddle with her beloved turquoise ring as she stood just in front of the Queen at the start of the event. Once things progressed and the princess was perusing gentlemen, Annabelle was given leave to eat and drink, while casting an eye to the Queen now and then. She left another guardswoman in charge while she took her meal and made a sweep of the room for security sake.
Once the princess shook her head at a few of the men, Annabelle had some vegetables and little bit of some kind of roast beast on her plate, and in a really unladylike show that would've horrified her Mayfair relatives, she ate as quickly as possible without sitting down, and without utensils. She seemed to remember that there weren't many utensils in this time period. Her fingers felt greasy and disgusting, and she found a serving man to bring her a little bowl of water to rinse her hands off before looking around the room again.
At least she didn't have to wear a dress. That was good. But as usual, her hair was stupidly ornate and her scalp hurt.