She's Luna, why are you expecting something else than a lunatic behavior coming from her ?
But anyway there's a reason for this, and it's a totally rational one ; proof that even Luna can be rational. She don't care about ranks, she will not respect you because of your rank, but because she like you. Listen what is said, by her and others, about her past. She'll call you "bitch" if she think you're one, whatever if you're the boss of another family, whatever if it can lead to an open war. And at the opposite, she'll call you "sir" if she like you, even if you're a totally unknown new guy she met quickly few minutes ago.
She dropped it quickly because she really like the MC, and like he act friendly, she decided to act friendly as well.
So, there's absolutely nothing wrong here. It's the opposite, it's completely accurate.
Please, take your place in the queue, we were here before you
I don't care, she smilled at me, I know she love me more than all of you 