I followed the Holloway case very closely. In everything I have witnessed with the Vandersloot family, Anita and Paulus were parents who encouraged their son to keep his mouth shut whenever possible, do not offer any helpful information, and just lie, lie, lie.
Imo, Anita is someone who would insist her son continue to do what he always has done, what Paulus taught him... lie about everything, cover up the evidence, repeatedly change your story to confuse the heck out of everyone, disregard anything that resembles doing the right thing, think of yourself first, and on and on. Anita, imo, is the last person who would advise her son to come clean and tell the truth.