In fact, Artoria canonically bullies magic users not named Merlin. Especially Witches, judging by FSN.
While her magic resistance is A, that's good enough to bully modern mages with their weaker magic. and while she can resist command spells unless 2 are used, the first one does require her active resistance as part of the deal.You mean like how Medea got her all nice and dressed up in UBW ? That sure was some bullying alright.
Morgan is from a lostbelt where she kept the age of gods going and managed to convert Rhongominiad into part of her magecraft. so substantially more powerful than any mage in the 5th grail war, including medea by a noticeable margin.