After Kronos went through the portal, Rosavellt followed him silently.
Rosavellt has always suspected that Kronos wanted the throne but she was never sure about it until now. His reaction to her statement told her everything she needed to know. She was now sure that Kronos sent her brother and Dulla here so that they could die and he wouldn't have any opposition to the throne. But Rosavellt didn't care. Rosavellt blamed her brother for his own stupidity and she blamed Dulla for trusting Kronos so much that she never suspected him. If Dulla was a little less hotheaded and more sensible, she would have known that Kronos was playing her like a pawn.
I will explain the reason for Andromeda's shy demeanor in a later chapter.