Millie's anger at both Jimmy and Miss Dorothy over their apparent liaison

Did Millie have the right to be so cross at the two of them when she saw Dorothy being beckoned into the room by Jimmy, and her then thinking they had become romantically involved? In spite of Muzzy's advice that she follow her heart, and that she now was taking it, all along she had said to the two of them she was a modern, not interested in love, and wanted to marry her boss, to secure a footing of equality with him. If you deliver that message too many times, obviously interested parties will seek love elsewhere, and much closer than you think. Of course, in the end this turned out to be all a misunderstanding, particularly when she saw it happening a second time, and finally had to investigate. Millie of course, earlier on, finally realized she was the one at fault here when she apologized to Dorothy, saying "After all I have my plans" The anger though with Jimmy lasted a bit longer, until she realized her boss Trevor Graydon and Dorothy, had been the ones setting their sights on each other.