Regina knew she was being irrational. She knew she could trust you, that you were loyal. But that didn't weaken the flame of jealousy that roared within her whenever she saw you with others. She didn't have any need to be, but she couldn't help it.
Regina had always been quite a possessive woman; awfully protective of those she loved. She hated the thought that those people might be taken from her, in any sort of way. That included you, her partner. The one person she'd trusted enough to give her heart to since Daniel. Alongside Henry, you were the world to her, and the thought of losing you tore her up inside.
That was probably where all this jealousy was rooted. On her break, Regina had decided to go to Granny's for lunch. And when she got there, she saw that you were there, chatting happily with Emma and Ruby. Regina couldn't take her eyes off you. Even as Granny tried to ask her what she wanted to eat, Regina was distracted by the sight of you so happy with others. The rational side of her knew that the interaction was innocent, but she couldn't put away the feeling of jealousy within her.
When Granny finally managed to pry an answer out of the distracted Mayor, she went about getting her order prepared. Once she had it, Regina gave a simple nod in thanks, before walking over to where you, Emma and Ruby were. A tight smile pulled onto her lips that she knew you'd likely recognize immediately.
"Hello, dear."
Regina greeted you specifically, before sitting down beside you without giving you a chance to react. You have her a puzzled look, wondering what the cause of her behavior was. The other two recognized it, too, Ruby raising an eyebrow, and Emma just looking amused; she was accustomed to how Regina tended to be about you.