How to deal with a rude, nasty teenager daughter?

[Julian]

My daughter, who is 19, is rude and nasty to me unless she needs money or wants me to buy her something. Then she is very nice to me. If I do not give in to her she hangs up on me, leaves and slams the door, etc. Do any of you deal with this type of issue? My mom always gives in to her giving her money or whatever she wants them to buy her. I cannot stop them and they have created a monster now. She "demands" things and tries to manipulate between her father, myself and my parents. I cannot tolerate this anymore but hate to have to "cut ties" with her until she matures. She is very immature for 19 years old. She lives with her father and stepmother because she and I do not see eye to eye on things. She is rude to my parents too yet my mom still gives her money. HELP!