Maybe it's because my Korean is limited but I didn't really hear her say
that she was bullied. She used the word "wangta" which means outcast.
From this I'm getting the feeling that she left because of a mixture of
problems. She was getting older and was tired of living with a bunch of
girls, the CEO kept on adding members even though she expressed her
dissatisfaction since she had to teach the new girls. I guess she didn't
feel appreciated enough for her efforts and Gaeun's addition was the
last straw. She didn't say that the members outright bullied her but
that there was friction that wasn't being solved because of the constant
influx of members.