thanks for all the helpful advice guys, I think I will forego making an apperance tomorrow and just sit back, not my problem whatsoever.
To clarify the credit card situation. My dad immediately called my mom after getting the bill assuming it was my sister that stole from him because she was the only one other than my dad and his GF that had been at the house during that time.
My dad wants to call the police, and the bank and claim fraud, which as soon as the bank does an investigation they will figure out its my sister, and the police will be forced to arrest her.
My mom is basically pleading for my dad not to call the police because she wants my sister to go to rehab and not prison for possibly a decade, so my dad told her if thats what she wants, shes (my mom) is going to pay him back the 10 grand if he doesn't report it to the bank.