She's saying that side-characters should be as such and shouldn't be the main focus of any given post or set of posts, seeing as the primary characters are just that - primary. Rather than making an entire plotline up for someone who may not even be used or go on missions (such as Bloom in this example) it's not really necessary to come up with and promote a dramatic storyline because that takes away from the focus which is, well, the X-Men.