Maybe it matters, maybe it doesn't but I had her at 17, so I've had a child with no money and no plan, and our lives are completely different to what they were...or probably should have been! So her citing money reasons is a bit of a punch in the gut.
Her citing money reasons is a punch in the gut??
In all posts, you have talked about your emotions, and how you have given her more money for babysitting than normal, that their rooms are not on same level, so she is not impacted by baby's cries.
What about her emotions? You are talking of money, how you are giving her more and than wondering why she wants to earn big money.
Her life is completely changed since her early teens, her mother is understandably busy with a very small child. But someone who was only child till 13, suddenly has her parents busy with a baby, classes etc.
She is a teen, she is in a emotionally vulnerable stage of life and her mother is not available.
It seems like, you have no time to even consider impact of all this on her. Also, maybe she is a bit jealous that her sibling has it better than she did as a young child because you are in a financially secure place.