I personally don't think it works - Other than the first letter they are completely different names.
I know people say if you drill it into them enough you can choose your own nicknames, but personally i don't beleive it.
I am a Jessica, my parents almost always called me by my full name. When i went to primary school i hated the nn Jess and whenever someone refered to me as Jess i would correct them, even when they wrote it in my work book, i would write 'ica' after it! When i went to secondary school pretty much everyone started calling me Jess, even though i had never introduced myself as that. It is almost impossible to correct every teacher, member of staff, friend, and friend's parents that ever called me that. I gave up in the end and just started accepting Jess, now that is what i introduce myself as, that is the name i generally use at work and on my work email and if i ever have to use my full name it seems weird to say it. My parents still mainly use my full name, and probably always will, but they are the only ones.
If you do choose Madeleine, i agree with what others are saying. You can shorten it to whatever you want - Molly, MiMi, Honey, Blossom, Petal, etc, etc (just as my parents still refer to me as Jessie-Ju sometimes
) - but don't expect everybody to call her that. Your Madeleine is more than likely to be shorted to Maddy/Maddie at some point in her life, and if you won't be happy with that nn, i personally think you are best off choosing Molly as a stand alone name.