It's not unheard of, you're right. When I lived with my parents we had a similar system once my siblings and I had jobs and were making money and were expected to help out. My spouse and I do the same thing now.
The difference is that we didn't go on Tumblr saying we were about to lose our house, didn't have food, and spent money on shit like Bronycon when money was tight. There were lots of things I would have loved to attend, but if I didn't have the money, I didn't have the money. I didn't beg for money with my sob story and use what kind people sent me on things OTHER than what I claimed it was for.
The fact that she did that, made her situation seem much worse than it is, flipped out at anyone who so much as gently suggested a way for her to make cash on her own, admitted to stretching the truth, and then posted this "oh boo hoo I have no money because I spent the thousands of dollars on shit I don't need but now I need help" once the hype on Tumblr seemed to die down makes it a, to me at least, 90% chance that it's bull. Not to mention what people have claimed about knowing her and saying her family lives very comfortably is still a factor in it (plus, I know the area she supposedly lives in very well and it ain't too shabby). I'm not denying that they have that many expenses, I'm denying that she's as bad off as she claims.
And if it isn't bull, and if they really are struggling, then Sats should've gotten a job ages ago, before shit hit the fan. She was bound to get found out eventually, and she really brought it upon herself.