Board Thread:General Discussion/@comment-31926729-20170618102307/@comment-25491743-20170618180103

It was stated that the apple has to be taken willingly for it to work, so that's why Regina told Snow instead of tricking her. We saw Maleficent force the sleeping curse onto Aurora and Zelena force it onto Dorothy in later seasons, so maybe a more powerful version was made, but Regina was unaware of it.