Pulcheria used her wealth for the [[Church]]. In doing so she inspired her brother to do likewise. While she appeared to be indifferent to the [[Arianism]] as practiced by the German tribes, she took a firm position on the heretical teaching of [[Nestorius]]. She almost immediately showed her antagonism towards him when he became [[patriarch]] in 428. Whether the downgrading of the status of the Virgin Mary from Theotokos to Christotokos under Nestorianism was involved, Pulcheria greatly influenced her brother's position in the controversies that led up to the [[Third Ecumenical Council|Council in Ephesus]] in 431. At first he was a supporter of Nestorius before acceding to his sister's position. In this controversy Patr. [[Cyril of Alexandria]] believed Pulcheria's influence was important in the downfall of his rival.
In 441, Pulcheria's influence on her brother began to wain as the eunuch Chrysaphius convinced Theodosius to dismiss his sister. But soon the [[Monophysitism|Monophysite]] controversy was raised by the [[archimandrite]] Eutyches and supported by Theodosius as well as by Cyril's successor as [[Patriarchs of Alexandria|patriarch of Alexandria]], [[Dioscorus of Alexandria|Dioscorus]]. When Eutyches' views were validated at the [[Robber Council of Ephesus|'Robber Council' of 449]] in Ephesus, [[Leo the Great|Pope Leo I of Rome]] included Pulcheria among those he approached for help in reversing the council's decisions.
On [[July 28]], 450, Theodosius suddenly died, and Pulcheria returned to the court as the wife of the new emperor, Marcian. She agreed to the [[marriage]] with the understanding that her vow of [[chastity]] would be honored. In 451, the [[Fourth Ecumenical Council|Council of Chalcedon]], presided over by Marcian, was convened. It condemned both Nestorianism and the [[Robber Council of Ephesus|Robber Council of 449]] that had supported the Monophysite [[heresy]]. The [[heretic]] Eutyches was deposed and exiled.