Terrible mom?

Recently my 18 yr old sis jess ran away from my moms house and is living with friends and at my dads house. My mom is mad at her so she turned jess’ phone line off. (thats why she ran away) but my 27 yr old sis whitney and my mom don’t know that jess and I are talking secretly when she has a phone handy. I have been telling her everything my mom and whitney say about her, which has made jess even more mad at them. But one day my mom whitney and I went to jess’ work to see if she was there, she wasn’t and I was glad. Jess does not want anything to do with them. Since my mom and whitney work together from morning to night all week jess sneaks home to visit me and sometimes has friends over to swim. I am always happy to see her since we are so close, we share all of our dirty secrets. So when we were on our way home I was driving and was defending jess and said some insinuating things to make my mom think about what she really did as a parent to make jess leave. My mom did not like what I was saying. But when we got home my mom pulled the keys out of my car and since I leave my phone in the cup holder whitney told her to take it too. So I said, “give me them back! … You just don’t want me to leave you like jess did!? Ya you just go ahead and treat me like sh*t and take my stuff away! That will make me love you more huh? … Well your wrong! You see how jess turned out when you did that?”

Now my mom wants me to apologize to her before I go to my dads house tomorrow and she is going to take my stuff to work! I have no such sympathy towards that woman! How should I buck up and say it?