Your sibling has a cheek. She knows that she is putting a strain on you... so, frankly, I would tell her where to get off, albeit politely. Something like "You know that I am not as well off as you and the others. You know I am single and supporting my kid. You nknow the parent could easily but this item, but is stingy enough not to, because she expects us to do it, maybe because we will be inheriting something. So... count me out." If that means they cut you off, you'll know that it was about pique, not just about money. Maybe they wanted to put you in a corner, just because they have money, and you don't.