You forgot the part where Mary is working directly with her brother, Mr Hamilton, to get the MC to marry into their family first. When she sees them the night before, they even talk about how she probably was already calling him as she walked away from Catherine's room. It isn't about swallowing pride- its about capitalizing on a situation that can play directly into their hand. And getting the meals there isn't difficult if you have a kitchen staff you can just wake up early and request breakfast to go.
I haven't checked myself, but you may want to look at the breakfast plates vs the plates used for lunch during the council meeting. I have a feeling they may be the same.