There's more to Mary Jane than a catchphrase. The version of the character I was introduced to, whether it's the newspaper strip or anything else wasn't associated with it.
And Kirsten Dunst's MJ never said it either. Nor does the Mary Jane of ITSV.
After all the Mary Jane that ultimately defined the character was Gerry Conway's, also Roger Stern and Tom Defalco, not Stan Lee's.