At the end of the day, I suspect something big probably did happen between Millie and Harley, given the subsequent split, her refusal to let him see him son and his reluctance to fight it.
However, it is not the place of anyone else close to Millie to try and reveal that. It lacks class. It's like that member who randomly came on claiming Millie was pregnant again. Whether true or not, you don't do that! Yet someone close to Millie, whoever they might actually be, constantly seems desperate to spill the beans. With friends/relatives like that, who needs enemies?