Except she already knew that the machine was dangerous during the rehearsal. And yet she was still willing to put Tina's life in danger during the actual performance.
And at the end of the episode when Tina turns out to be okay, everyone's basically like "well, Tina's not dead so there's absolutely no reason to get angry at Louise for her complete disregard for her sister."
I honestly can't think of a single time when Linda or Bob get angry at Louise. At most, Linda's frustrated that Louise and her aren't close, but she never punishes Louise or gives her boundaries. Meanwhile, when Tina starts talking back, getting in trouble in school, and sneaking out, Linda reacts like a normal mom.