Yeah people are definitely mischaracterizing her here. They’re acting like she went “I know , I’ll threaten my sister and get her to give me money!” rather than what actually happened, which was the sister making up both sides of the scenario in her head and then just taking the money her sister offered her.
"Please don't tell Mom! I'll do anything!"
"*Anything?* Eh...? Alright, there is one thing I'd like from you..."
This is literally what's on the page. There's not much room for interpretation.
For the record, I, at least, am not suddenly in a position of, "Wow, I now hate this story and character." If anything I find it funny just how low she's gone. But I must acknowledge that it is horrible of her.