go to this youtube...there are a person tell a reason why she has less part....
this is what the reason:
Because Boram has poor health and she cannot sing very well while she is dancing... Thats why she always gets little parts... Its not her company's fault, she requested it.
Boram has a very good voice, thats why CCM got her into T-ara. So she still records her part in the CD, but she might give some of her parts away in a live perf.