Can a mother decide whether a baby will be born male or female through careful control of her diet?
In short: no.
There is, as you point out yourself, some research shows that (pre-conception) diet can be an influence, but nothing more than that. The mother definitely can not decide the gender.
I had a hard time finding research that replicated this result, only links of more news-like sites that refer to the paper you already linked.
From a BBC news article (emphasis mine):
Dr Allan Pacey, an expert in fertility at the University of Sheffield, said there was good evidence that nature had subtle ways of changing the sex ratio of a population in response to a variety of circumstances. However, he said: "I would urge women to not to start starving themselves in order to try influence the sex of their baby. "It has been observed in some animal studies that even small changes in female diet can affect the life long health of the offspring, so it is important that the mother has appropriate nutrition at the time of conception and throughout her pregnancy."
So from this single article alone I would conclude that although there is an influence of certain factors on the sex of the child (food being one of them), there is no way (and certainly no safe way) to decide the sex of your child.