Long enough to realize that Yukari was talking to her tanks instead of the friends that she seemed to have brought over.
Notice the tray of drinks - it seems Yukari's mom overheard her calling out to Miho and the others and had assumed they were there... only to find out otherwise and ended up standing there awkwardly for a bit.
"No, sweetie, I did not see you playing with your tanks again."
But Mom you were right there
S t a r e ⋮
Yukari-san working out how she's going to play around with her models(Imitating her voice)If the scene is like this......then the enemy should be like this...She becomes more and more impas-sionedNishizumi-dono! Over there!Got it, Yukari-san!Hana-san, aim right in front of the enemy!Mako-san, turn left at the crossroads!Roger that ~~But Nishizumi-dono, that's where...It's alright Yukari-san, that's...It's Independent Training