I Broke My Sister's Phone Silently

So last week I was really frustrated with my older sister for always hogging our family room. She's the type who leaves her phone lying around like it owns the place, and one day when she wasn't looking, I picked up her brand new iPhone and dropped it from a height of about two feet onto the hardwood floor. It made this sickening crack sound that told me exactly what happened. When my sister found out later, all I could do was say sorry over and over, but the look on her face as she saw the shattered screen still haunts me. Every time I see her crying or trying to fix it, I feel awful.