Question on Legislative Management?

The Carol Aloisi story was in yesterday’s Globe, but no one has stopped to ask about how legislative staff gets hired.

From the story, Ms. Aloisi was “was assigned by DiMasi’s office to work for Springfield Representative Cheryl Coakley-Rivera in 2005”. Then, “his office reassigned Aloisi to Kaprielian’s office in August”.

Next, Garrett Bradley shows up, finds her in the office and puts her to work. “Aloisi came with Bradley’s new State House office assignment in February, the lawmaker said.”

Are legislative staffers typically assigned by the Speaker’s office? Do individual legislators not choose and hire their own staff?