This episode has reinforced the belief I've had since season 1 that for all her talents, Sena is INCREDIBLY gullible and kind of an idiot (in a very funny way
).
I'm pretty sure she gets it from her father.
If Kodaka wasn't in the picture this series would have gone down the yuri route ages ages ago, I don't know how long Sena has had those pictures of Yozora in her room but considering she looks at them everyday well.........