Antenna at full power so she can sense people coming and dump Mordred off her lap.
After watching lots of Cooking with the Emiya Family, I've come to realize it's both a means to show her mood and a sort of radar/sniffer, ready to point out when Shirou is close to coming home. :P
Oh god, imagine Shirou, Rin, Sakura, & Rider coming upon this scene. :D
