There was a reason why Heaven tried to be a good in-law. It wasn't because she wanted to be accepted by the family or create a picture-perfect family. Her reason was simple. Heaven had a soft spot for the elderly.
After losing her father, the only parent she had, the older adults that came into her life were from Dominic's family. So, even if she hated Dominic to the core and couldn't even look at her son, she didn't treat the older generation of the Zhu family the same way.
Heaven didn't try hard to return their affection, though. All she did was listen without saying what was on her mind or being meek like she had always done. This was the first time she tried so hard to appease the Old Madam. For sure, if this was the original Heaven, she might have not said a word.