Sibling Problems can someone please help?

My siblings do not have much. In any aspect. Money, belongings, cl, etiquette, etc. I do not understand why they are like this. My mother did not raise us to be worthless idiots yet for some reason 3 of the 5 of use turned out to be. My sister is a terrible mother and person. (I'll just let it at that) she is constantly needing and borrowing. For a long time I refused to lend her money or much else because she would make empty promises of repayment or whatever. I use to lend her my vehicle but she would be gone for hours then bring my vehicle back on empty and a few times with damage she even loaned my vehicle to others. Now, my mother or I run her instead of trust her with the vehicle (she has a van but it rarely runs). The one thing I did do is give her an apartment in the building my husband and I own. One reason was because of her children (I do not want to get into it). She owed me $50.00 rent for this month. On top of that I bought her diapers, and a pack of cigarettes. (I know I shouldn't have) She was to pay me the money today. My mother used my vehicle to take my sister to the bank and to the store (she received her child support today) There were 2 things I asked for. 1. pay me the money I'm owed and 2. replace the gas that you use. She did neither. She paid me some of what she owed. But not all of it. I am very angry with her. Mostly because I lost my job about 7 months ago and things have been very tight. i cannot afford to just hand things over to her. She called me and asked to use my car to go to a town that is about 25 miles away (one way) because she wants to try and sale some pain pills she has and she'll give me gas and pay me the rest of what she owes me. I told her no. She began screaming at me and calling me names I simply hung up. She and my brother are always doing this to me. Then they make me feel so badly all I want to do is cry. She claims she could not pay me and get my gas because her cell phone bill was high and took most of her child support (which is a nice sum of money it is only a couple hundred less than I live on! plus she has other money sources!) I hate the way they treat me. I can't even believe she would ask me to give her my car to sale pills. Its ridiculious. I am against drugs my husband and I do not do them or anything i have no respect for anyone who has to turn to drugs. It makes me so sick! As if that did not make me angry enough she started promising me more monye and more gas if I let her go sale them. First of all why would I want dirty money? I am not that kins of person. Secondly, what if she didn't sale them? Or, if she was arrested? Then what? I have recently been diagnosed with PCOS. I have a dr's appointment tomorrow. I have explained that if she uses all of my gas then I can not go to my appointment which I need to go to, to get my meds. She claims she'll get money and everything will be fine. I still said no. How do I deal with my family?! I feel like I am losing my mind. (I especially wnat to know how to stop the rude comments about me and my husband. They are always so ignorant when they don't get their way and it hurts. They are suppose to be my family! Family does not treat family that way1)