Mantaren

First of all, Choi Soo Young & Kim Yoo Jung don't even look that much alike. Even if they did, Sooyoung is 9 years older and became well known and has had a very successful career way before Yoojung, so Yoojung would be the one being another version of Sooyoung and not vice versa. Check the facts before you spam with rude and ignorant comments.

Then just don't watch it. Whining for no reason...

People are acting as if she's being forced to play into an abusive relationship with an old pervert. She turned 19 in September, so she's considered 20 in Korea, which is the legal age of consent in South Korea. Also, she's an experienced actress that has played many roles before and she's playing a young adult in a Korean drama, a role to which she has agreed and for which she has signed a contract. Not to mention it's probably going to be a platonic love like always happens in Korean dramas, with nothing explicit taking place with such low age rating.

Things have not progressed enough yet, but by the looks of it there could be a love triangle. It looks like both the first and second male leads like or are starting to like the female lead.

His character and his acting seem way more interesting and refreshing than the first lead's, to be honest. It's a good thing to see his acting has improved.

They won't lose their powers if someone finds out about them being witches, their powers will start getting lost if they are betrayed in terms of love. It's not about the lover finding out, it's about betrayal.

They're supposed to lose their powers when a human betrays them and their love, so she started losing her powers when her boyfriend cheated on her with that obnoxious pork restaurant owner lady.
Plus he was not with her from an honest place, he just wanted to be with her because he thought that since her family runs the famous soup place they'd be rich (she doesn't know that, but his coworkers were discussing it).