The word stepmother 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™ Plays In The Letters stepmother
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Seven Letter Word Alert: (25 words)
emoters, heptose, heteros, meteors, mothers, pothers, potters, pretest, protest, rehomes, remotes, rosette, smother, spotter, stomper, strophe, tempers, tempest, tempore, tempter, tethers, theorem, thereto, thermos, treetop