Hmm. I'm tempted to add a translation note saying "gone standby all the way", but don't want to do it as I'm unsure, so I'm just commenting so someone may confirm it and add the note.

It makes sense, though, if you consider the album this image came from. She's always playing / getting raped / having a good time there.

Looks like the expression「スタンバってました」is a Katsura Kotarou (Gintama) quote or meme of sorts.