Boss's Daughter ?????

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I work for this company is almost 3 years and I enjoy it .. But recently i got a job from Him that I should back up his son and Daughter to build new bakery store . I got new problem that His son is not to care about this store and his Daughter is to Bossy that she always act like big boss until there is my Boss is around that new Bakery store. I think it was very u professional, in case if this store is not work out it my boss will blame to me . Please give me some best way out to deal with this problem ??? Should I tell all the true to my Boss or let it be, or may be another way ????