What would be the theological reasoning as to why she was denied communion?
Insufficient synodality score.
In distributing Holy Communion it is to be remembered that “sacred ministers may not deny the sacraments to those who seek them in a reasonable manner, are rightly disposed, and are not prohibited by law from receiving them”. [177] Hence any baptized Catholic who is not prevented by law must be admitted to Holy Communion. Therefore, it is not licit to deny Holy Communion to any of Christ’s faithful solely on the grounds, for example, that the person wishes to receive the Eucharist kneeling or standing. -- Paragraph 91
Nothing theological.
It’s 100% ideological.
The bishop is a dyed-in-the-wool arch-modernist.