I think you'll get a hell of a shock.
My sister (I am nc but not because of just this) is also ridiculously irresponsible with money.
My parents always bail her out, she is a single mum to 3 DC and doesn't work but has a new car, several holidays and long weekends away a year, dresses DC in expensive clothes and shoes, buys branded groceries and goes nuts at birthdays and Christmas on presents for DC.
I've given up saying anything to parents, more fool them.
My mum is genuinely worried that when they die and are no longer around to bail her out she'll end up homeless/bankrupt (she won't - she'll find some other mug to bankroll her - not me).
Does your sis have DC? Do her and her partner actually need the size/quality/location of home they have? I highly doubt it - meanwhile you and your family are struggling. She CERTAINLY doesn't "need" several holidays a year. And I bet her clothes and shoes and haircuts and food are all high quality too?
Plus her partner sounds more than capable of working.
How old is she? She needs to grow the fuck up do a budget and stick to it!
Is she working?
I hope when you calculate the full amount you get ANGRY because she has CONNED you.
She's not loving, kind etc she just knows what side her breads buttered!!