Yes, Sophia lied when she had to leave the wedding event to protect her son for Aiden, who blackmailed her with sexual favors. That puts the lie into perspective. And yes, a woman would probably call her friend right away to find out how this important event turned out. Whether she is satisfied with her decision. But the game is being developed by a man. We always miss such subtleties.The Sophia thing, actually Sophia is no angel to begin with, so I am not siding with her on not calling her friend, that is bad friendship.
The instance you mentioned of Liam is when they arrive, I mentioned ones that happen later on in the story. Meaning they hold more weight. This is how liam is now, in a similar manner you would say that Sophia will never cheat based on what she says on day 1 but the present Sophia is completely different. Hence judging Liam how he behaved then isn't right when he has clearly shown signs of change for the better
But perhaps the knowledge of the invitation is also used as a narrative medium. The call comes at a time when Sophia is about to give in to Sam's advertising and wants to do something really stupid. To put your marriage at risk for a 17 year old romantic. The call could act like a reset switch and bring Sophia back to reality. For now!