Hi dolphinesque --
I've only ever posted regarding Greek food since that's become kind-of a specialty (I live in Greece) but my HOBBY is wedding cakes, in particular decorating them which I love!
A quick answer and then you can let me know if you want more info:
IF (and it's a big "if") your daughter is experienced with cake-baking and has a high success rate, making a wedding cake isn't all that impossible, however, assuming this is her first wedding, does she realize that she'll have plenty on her mind those few days prior to her wedding?
You mention marzipan -- does that mean you're writing from the U.K. where that's more traditional?
Either way, it would be useful to know what exactly she's envisioning. I presume more than one tier, right? Do you know if she wants stacked or on pillars? Does she want a soft icing or does she want rolled fondant?
She would be WELL advised to practice ahead of time -- does she have time to do that?
Also, what size are we talking about? For how many people?
Let me know if you'd like to pursue this!