My dude i have read wolfheart and saw the build up to the audience, they smelled a great change in the air and decided to try to be of use, tyrande accepted them back with a bajilion restrictions to their sorcery and practises because of their USEFULLNESS.
It wasnt because they wanted to reconect or mend a cultural rift, because the highborne were under a severe leash to prevent their stupidiy from lashing out again, they were accepted back for pragmatic reasons.
To the point they dont even care how many maiev killed in wolfheart, because they are of such low importance that maiev is more valuable.
Hell maiev could have killed each and every highborne and i can bet that tyrande and malfurion would STILL accept her again, thats how little they care.