I think the other thing to remember in this situation is that the sister may have financial obligations that prevent her from helping. People hate to talk about money.

Also, perhaps the sister and her husband has a "no lending money to family" policy. She also may think you have access to resources that you haven't accessed yet.

If you haven't, ask her for the money. People can't read minds, and sometimes we have to be very clear about what we need. She still may not give you the money, but then you'll know where you stand with your sister.