Sandy hates to feel controlled. It's not surprising when you think about her Domme side. Her lovely boyfriend was constantly telling her that I'm controlling her, that I'm a dominating character. He did it because he wanted me to let him see even more of her and hoped she would push back. He also thought he was helping someone he cared about improve her life.
Marriages are subtle things. We make compromises and adjustments, nothing is perfect. I can be a dominant character which is why being Sandys sub worked well for us. It gave her back a large measure of control. It brought us close and brought intimacy to us without too much pressure for sex. But he made her suddenly hyper-aware of the compromises she makes. The man with two failed marriages was needling her about how she should not need to compromise. And in her stressed mental state, while consciously she was rejecting his statements, subconsciously they were making her feel more dissatisfied.
Guess who offered her an escape? We still both wonder if these games he played were on purpose to see more of her, or if even he in his weakness (he isnt a strong person) didn't realise what he was doing or why.