It might have been tactless, but I don't think it was mean-spirited. The kids were literally asking about it and she just told the truth. It's not like it was some big secret.

I didn't remember her wagging her finger so I went back to re-watch it and I still don't know where she wagged her finger. I'm guessing you meant the shush gesture she did with her finger - which isn't the same as wagging it at someone. And while it is also condescending to shush someone, she wasn't really using it in that way, either. It wasn't "shush, stop talking" because Mirabel wasn't saying anything. It was more, "I'm about to tell you something in confidence, but shh, keep it quiet." Not the same connotations at all.

Meh, fair enough. Although I'm not sure why people blame her for keeping quiet about Bruno but also blame her for not keeping quiet about Mirabel. She gets blamed whether she tells a secret or not - which I actually think could be an in-universe element of her character worth exploring in the upcoming season. Where she gets blamed for telling secrets AND also gets blamed for not telling secrets and so is given inconsistent messages about how she's supposed to use her power. One of the reasons most people don't want her power - who wants to be held responsible for so many secrets, and having to balance the consequences of telling or not telling for each one?

Eh, siblings are sometimes rough with each other.

I didn't really see it this way. She was just eager to take the opportunity of the moment. I'm sure she was grateful to Mirabel and showed it later, but she needed to take advantage of the moment Mirabel was giving her, otherwise what would be the point of Mirabel giving her that moment to begin with? Again, maybe a little bit physically rough but Sims families are just like that. It's nothing hurtful.