If you like Marley, how about the spelling Marlie, or Mahlie? I think it de-associates the name with Bob Marley.
I LOVE Mahlia.
Or then there is Maely, Maelie, Maylie, or even Maelyn.
I also like the name Madeley - although I guess you couldn't have that because of the Maddie factor....
Myra and Maia are nice also.
Mmmmm- lots of nice M names....