"I want ninety-one lemons."
Translation:Dw i eisiau naw deg un lemon.
Firstly, I think she does and one would. Secondly, I am struggling to find any possible misconstruction for Dw i eisiau naw deg un lemon. Languages will generally find a way to clarify where confusion could arise, but I cannot see that that applies here. I think the speaker's requirements are equally clear, specific and bizarre.