I'm not even saying that Sam would "break her heart", just confirm what she always logically knew, but allowed herself to ignore for the sake of a steamy fling. She's said a million times now "I'm a married woman who's more than twice your age, I'm your parent's best friend, and I'm your best friend's mom" to Sam, which means that deep down, she knows that this thing is never going to work in the long-term. It's not like she's going to abandon her life, and run off with some 16-year-old kid. They'll have some fun for a while, but it will end eventually.
"This story is about Sophia ; not Sam and Sam is not the only LI or route for Sophia"
That's kind of my point. This is Sophia's story, and with all these branching and diverging paths, L&P is going to have to eventually streamline everything back before he brings the whole thing in for a landing. He's not going to write an ending for all those individual LIs, and all the variables within their own storylines. To visualize a story like this, I guess it could be like a lemon, in that it starts pointed and narrow on one end, gets wide in the middle, and then comes back to a narrow point on the other end. Mass Effect and The Walking Dead are some that I can think of off the top of my head, and those are large studios with staffs and multiple writers, not one guy doing everything. I can promise that whether you went the Filthy route, or stuck with GW the entire way, all roads eventually lead back to Liam for the final curtain call. Some roads will just be dirtier than others.