Well, it’s totally a moot point, because nobody is going to go back to the greek gods. But historians of religion do note that the monotheistic God of Judaism, Christianity and Islam is a particularly jealousGod ... he doesn’t get along with other pretenders. As such he’s more prone to promote ethnic divisiveness.
Polytheistic religions did to a certain extent tend to have less specifically religious violence, since a polytheistic pantheon can more easily be rejiggered to include the other guy’s deities as well. (Or to see them all as “avatars” of each other).
Of course, there are modern-day monotheists who do something similar, by claiming that all the monotheistic religions worship the same God. That’s perhaps not a majority position, but it could be. The problem is that monotheistic religions really can’t take that stand in relation to polytheistic ones ... while polytheistic ones can view monotheists as worshipping the “king” god, like Zeus or Jupiter.
So there is something to what she’s saying.
There’s the additional problem that in fact Catholicism is a polytheistic religion. Not only does it worship a tripartite God, but it also worships Mary and the saints. This is monotheism in name only, and it is quite jealous.
But anyway it’s totally a moot point.