How to handle a difficult sister who always appears to be jealous?

You can't just avoid her forever because if you do, there will be hatred for each other that will stay in your hearts. You must talk to her calmly and tell her that you are not stingy but also tell her that because of the economy she must not always spend her money on items that are very pricey and must also not envy others. Whatever we have be thankful for it and don't forget to bless others with your blessings. Even if there is deep hate between you two, I really know that there is a place in your heart where you still love your sister. Also seek guidance from God so that He may help you deal with the problem that you have. Everybody knows that nothing is impossible with God. I hope you can restore friendship with your sister.