Sorry, I'm not buying it. Sure, she rejected him when they were dating, but so what? She eventually gave in and married him. I think she just wanted to make sure he was for real before getting involved with him.
The thing with Chris' parents...first, as the documentary showed, they never liked her. Yet she still tried to keep them in their lives, including their grandchildren. But his parents apparently insisted on bringing foods in that one of the girls was allergic to...classic "I'm the grandma and I know best" BS. Sure, Sha'nann probably shouldn't have blown up at them, but it was only right that she draw a boundary to protect her daughter!
Was she pushy? Maybe. But she also clearly loved him and wanted to make their marriage work. He was the one who refused to go to couple's counseling. And what I saw from the footage and all the evidence available, was that he was passive aggressive - rather than simply being honest and saying no (to whatever), he'd just go along, and then stew in resentment until he let it out in some random, unhealthy way.
Being a "difficult" person is a matter of perspective. From what I saw, she didn't seem difficult, but rather, motivated. If she was pushing them into a lifestyle he didn't like, he should have said something and worked with her as an equal partner together. Not letting her take charge of everything "as the woman" then just acting out like a petulant child.