She would have started a war regardless. Anduin getting enthroned was just a convenient excuse.
Anduin was Varian's "conscience" it was him who advised him to be more open and less angry. So, "let's trust the person who has a reputation for being a warmonger and aggressor more than the person who talks and acts peace all the time."
Her reasoning is clear BS and a weak justification of her personal beliefs, which are "fuck everyone else as long as I get mine!"