T-ara and Bullying

A lot of fans of T-ara, one of famous Korean girl groups, have been gotten very angry about Hwa young's recent departure caused by her being bullied by the rest members of the group.

The last line could also be:

...caused by her being bullied by the other members in the group.

The conflicts started as some members posted tweets in unison on their Twitters accounts, giving an the impression that Hwa young had been the target of bullying by other members.

Although the management agency Hwa young once belonged to, Core Contents Media, officially announced that there was never any bullying, many insiders and reporters of entertainment told that Hwa young had been an outcast since she started being a member of T-ara in 2010.

The management contracts between Hwa young and Core Contents Media was terminated as Kim Kwang soo, the boss of the Core Contents Media, released an official public announcement.

To make an idol group, management companies hold auditions and search for someone with not only a great appearance but also a great ability to either sing or dance.

To make matters worse, usually when Idol groups start their career as an entertainer, the age of the members of the group is usually teenage.

It might sound more natural to say:

To make matters worse, usually when Idol groups start their careers as entertainers, the members of the group are usually teenagers.

Almost every idol group has a rumor that some members have been embroiled in bullying or other scandals.

"to be embroiled" is not a very common phrase, so you might want to say:

Almost every idol group has a rumor that some members have been involved with bullying or other scandals.

The downside of the relationships among idol members has finally been revealed to their fans.

By manipulating the medias, as it always does?

It seems that there needs to be serious consideration and a long-term solution about both to prevent this from happening again, and for K-pop stars to recieve more love from their fans.

Many fans are very disgruntled by the scandal because the problem of bullying is a very serious issue in Korea.

Because "problem" and "issue" are nearly synonymous, there's no need to write them both.

Why did this incident occur?

"incident" sounds kind of newsy or a bit proper, whereas "happen" is kind of a common word. Changing "happen" to "occur" makes it match a bit better. If you want to use "happen", you could write "Why did this happen?"

This bullying scandal shows us the dark side of the entertainment industry.

To form an idol group, management companies hold auditions and search for someone with not only a great appearance but also a great ability to either sing or dance.

Once they are chosen as a trainees, they have to practice extremely hard to debut as an idol group.

During/Throughout the rigorous training process, they have to practice singing or dancing with other trainees who have a very different personalities or who may be jealous of them.

To make matters worse, the majority of idol group performers are in their teens.

Almost every idol group is rumored that some members have been be embroiled in conflict or other scandals.

"embroiled" is actually the perfect word here, but your use is a bit off. What comes after "embroiled" is a noun that generally has not been converted from a verb. In other words, the gerund (-ing form of a verb) cannot usually be used after "embroiled". I have changed "bullying" to "conflict" here, but you could also say "embroiled in bullying scandals" where "scandal" is a pure noun.

The dark side of the relationships among idol members has finally been revealed to their fans.

"downside" means "disadvantage", which isn't really appropriate here.

A lot of fans and admirers have turned their backs on T-ara , some have even become "anti-fans".

"followers" is almost always a religious word, similar to "disciples".

Will they manipulate the medias, as they always do?

Usually we refer to companies as "they".

Also, "media" is the plural form of "medium". A medium, among other things, describes a way in which information is delivered. A newspaper is a medium, as is a radio. Radio and newspaper are two media used to relay information.

If it does, the bullying issue may gain momentum.

I'm not sure exactly what you mean when you say it will gain momentum. Do you mean to say that it will become more important in the media?

It seems that there needs to be serious consideration (of what?) and long-term solutions for about both to prevent this from happening again, and for K-pop stars to receive more love from their fans.

This is a little unclear as well. What do you mean by "both"?

It seems that there needs to be serious consideration and long-term solutions about both to prevent this from happening again, and for K-pop stars to receive more love from their fans.

I am correcting this again according to your explanation. However, I think that you could eliminate "serious consideration" from the sentence and still have the same effect. I think it's a bit awkward to write it because "consideration" is about thinking, but "solutions" are about action. Since this is a serious issue, action seems the best course.