Of course Saber is getting ready to eat or in the process of eating something. Honestly I don't think there is that many comic panels in which she isn't doing so.
As for Mary, I guess this is some sort of payback for trying to disrupt the one time where Saber was the focus and not eating, with food.
>Yachie: Won't apologize. >Saki: Won't apologize (But is close to do so). >Yuuma: Will apologize (After many excuses). >Keiki: Won't apologize (And neither Mayumi).