Sounds like my SIL. She and her husband, my BIL, both quit school and have no education and have never had a decent job. My DH has a college education which he got through the GI Bill. Every time we get together she is always talking about how "rich" we are. We are a long way from that but we do get by.
No one can take advantage of you it you don't let them. I would be very firm and tell her what she can or cannot have. If she gets mad, so be it. She'll get over it. As long as she thinks she can get what she wants from you she will continue. Hang in there and be firm.