WELLESLEY, Mass. – Janette MacAusland’s life looked like a postcard – a beautiful family, a $1.5 million home in one of the richest suburbs in America and a successful career. But behind closed doors, her world was crumbling. Her marriage was failing and her husband was fighting her for the house and the kids. Now, the mom who seemed to have it all is accused of slaughtering her two young children – leaving even those close to her reeling about how such horror could allegedly hide in plain sight.  “When I heard the news, it was probably the biggest shock of my life,” one of MacAusland’s friends told The Post.  Kai, 7, and Ella, 6, MacAusland were found dead inside their family’s Wellesley home last week — where their mom allegedly confessed to strangling them. Janette Reber / Facebook “I couldn’t process it. I’m still trying to reckon with it. It doesn’t make sense.…