She has full free rights to disagree with her son, who has the same right to make his own decisions. Each come to their own positions from their own experiences. I would be sorry to see the family dynamics so far destroyed, but support each one of them holding their positions.
So, you support her son’s participation in the unjust and meaningless war that took lives of over million people?
I guess, in 1939 you would’ve enthusiastically expressed your support for Hitler’s wars, as well. There is no moral equivalency between Ukrainians fighting for their country and Russians, who started the war and were methodically annexing Ukrainian territory since 2014.