It totally is and honestly, in my opinion they could each have their own harem and I wouldn't care. Too bad idols aren't supposed to be in romantic relationships.
I wonder if it's actually written down in their contracts. If yes, then well. Break of contract.
I feel like it's probably written down vaguely and just talks about maintaining a certain image. I still don't think they're gonna break her contract, though.
I don't think they have that option right now... Especially after the Rio incident. Plus it seems like such a waste. They'll probably just punish her by giving her no solo lines and shoving her to the back more than she already is.