It looks more and more like Jason was genuinely in the marriage, having given her parents 45 thousand dollars for the wedding, sharing banks accounts with her, the house, the car, the money for furniture, and she doesn't even share an address with him. My impression is that from the outset she wanted children - and his children were good enough.
It looks like she recognized him as a perfect, vulnerable victim, manipulated him into moving to NC, into marrying her, and the final act was to adopt the children. Had she succeeded, she would very likely have divorced him, taken the children, and most of his money. When she realized that he was not going to let go of the children, she decided that she would be more successful if he was dead - and so she and her father drugged him and attacked him while he slept. After the murder, she sent adoption papers to Ireland. That didn't work. Then she launched into a full on custody battle.