The word grandniece is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 18
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (24 words)
adenine, angered, cairned, cannier, carding, craning, cringed, dancing, darning, deraign, derange, earning, engined, enraged, generic, grained, grenade, grinned, nearing, needing, reading, recaned, reigned, rending