I’ve never seen the film…
But a commission is a commission. And vegan with gluten free is no walk in the park. I can do GF with my eyes closed but smbc does NOT work sans eggs and sans butter. I made my own fondant (no MMF either) and made the buttercream with cocoa butter and soya sub. (Earth butter is not available where I live). The result was fairly unstable and I should have put a roll of fondant around the edge of the filling to hold it as it subsided and bulged on the top tier.
Also, I did this design from a photo and it was the last time I plagiarised anyone elses work; I apologise profusely to the original decorator.