I actually felt awful for both B & T in that video. Betsy clearly frustrated at Lula expectations of help. Two sisters bickering, but instead of actually mediating R is encouraging Lula’s demands of Betsy to help and placing all expectation onto her 16 year olds shoulders and no one is listening to Betsy saying she’s tried and doesn’t understand. So, she’s 16, done a shift at work and gets ratty with her sister.
She clearly then gives in, tries to help while the actual parent sits there doing nothing and grows more and more frustrated so gets more pissed off with Lula.
It’s so obvious she can’t say what she wants to her mum so her sister takes the brunt of her annoyance. But most telling of all is the fact Lula seems to not even have bothered asking either of the adults in the house for help, but has gone to the one person the kids can all rely on, Betsy.