Admiral proudmore (jaina's father) saw all orcs/horde as savage animals that should be exterminated, since he expected they will attack again once they recuperate/rebuild.
Jaina in TFT believed orcs and the rest of horde can coexist with the alliance-oriented races and that they would not cause another great war or genocide.
However after all that the horde has done since War3 jaina has come to believe that her father was right and that only exterminating the horde can bring peace to azeroth.
I dont think there was any change of lore or history there.
Admiral proudmore wanted to exterminate the horde in order to prevent another great war, and now that such a great war & genocide is again happening Jaina finally agrees with her father.