hi
i agree w sparklekitty and fathom.
your ah is using your sister as a tool to control you. she was looking out for you (maybe not the best way to go about it) and he used the fact you confide in her as an excuse to be mad at you and accuse you of something nefarious. it is blameshifting. ignore the fact he was a jerk and focus on you telling your sister about his actions.