Headcanon: Selina has heard Bruce vent about his kids many, many, MANY times. She can even tell who he’s talking about by the first sentence, as detailed below:

He’s just SO - Dick
WHY does he - Jason
He NEVER - Tim
She ALWAYS - Cassandra
I don’t UNDERSTAND why he - Damian

When his back is turned, she’ll mouth the rant and sometimes mimic his body language. One time he caught her dramatically shaking her fist and so she just fist-bumped him.