My sister's boyfriend..?
It's hard to imagine her sister knowing such a person. But, quite some time has passed since Shaarya last saw her, so who knows? The last few years, Shaarya didn't visit home at all. It's not that she couldn't, her academy isn't that strict. But it was more to do with the fact that she refused to do so. Shaarya would not let Mother and the rest of the family continue acting like terrible people. When she was old enough to understand her sister's situation, Shaarya left home. No matter what Shaarya said to try to convince them to change their minds, they didn't.
So Shaarya refused to stay in the Mist Kingdom. She picked an academy that's in between the sun and rain Kingdom. A reasonably decent village, with an excellent academic school that provides military training too.
Even if she was making a point, Shaarya didn't want to sacrifice her skills.