Karl was not emotionally or psychologically healthy when she got pregnant with Isaac and ten years and three children later, she is still not.
So many viewers watch this show and see the resources these women have to better themselves (namely, large amounts of cash) and we can't imagine why they don't, but there are many, many people in the world who have lots of material resources who have serious mental health problems. As I have said in the Tori Spelling threads, wealth can be a protective factor against the negative impacts of mental illness. Janelle is a good example in the way she has used her wealth to protect her in the legal system.
Karl has been coasting along, with her wealth somewhat protecting her, in the sense that she has financial security which allows her to leave when her relationships go south, and to live in safe neighborhoods. But in the midst of that, she keeps birthing children, and they will all be the witnesses to her dysfunctional ways.
Hopefully, at some point, maybe when her kids start showing problems, or when her high income drops, or maybe just due to getting older, she will choose to get real therapy and be honest with herself and the therapist and actually change. Until then, her life will be filled with the drama she creates.