Lies

It was my dad's birthday today and my step mom and sister came over for dinner and to celebrate and they slept over. At night my sister and I were talking and goofing off when the conversation turned serious.
"By the way, I was gonna tell you this, but I didn't know how you were gonna take it..." She started.
"What do you mean?" I asked, very intrigued. I love when a sentance starts out like that..
"Well before you came home this summer we went to the cabin to clean it up, and on the beach [my step mom] started telling us all these things, which I'm assuming are lies."
"Like what?" I asked, starting to get angry because this is the millionth time I've heard one of my step moms lies.
"Well she said that you tell her more than you tell your dad, and that you do all these drugs and she 'knows' you do heroine, and said that she saw a picture of you on the internet having an orgy with 4 guys.."
"WHAT?!!?" I couldn't beleive it.
I don't know which is worse, the fact that she made up the most ridiculous lies or the fact that my dad beleived her!
A couple days later I came home and my dad asked about it.
"So I know you were drunk last night, but I didn't smell alcohol on you when you got home... Are you sure you weren't high?" he asked.
"No, but if you want I'll pee in a cup for you to prove it." I replied sarcastically.
"I want to beleive you but.."
"But what? Just because [my step mom] feeds you all these bullshit lies doesn't mean you have to beleive them."
Then he started denying, and finally he asked where I heard that she said that and I said [my sister] and he said, "Well you shouldn't beleive [my sister] she causes drama too... Anything [my step mom] said [my sister] just agreed with."
So now I don't know if my sister lied about it, or if she's following her mother's example of lieing or if my dad just made that up to save my step mom's ass.
Who knows? Who cares. My dad's ex girlfriend (who I still talk to) and I think that my step mom is textbook example-ly trying to get rid of me and make me not come home again. Well it's working because if this is what I get whenever I come home, than noooo thank you.