My Bestie Married My Boyfriend

On Valentine's Day, Nina discovers that her boyfriend Jasper has been secretly married to her best friend Vivian for five years—and they have a child together. Devastated by their betrayal, Nina loses her own baby in an accident. After waking from a coma, she cuts both of them out of her life and disappears to the countryside.

There, she slowly heals, finds new love, and rebuilds herself. Meanwhile, Jasper and Vivian lose everything—including their son—and spend the rest of their lives haunted by regret, watching from a distance as Nina walks away without ever looking back. Let me know if you'd like a shorter or more polished version.