A married daughter was like spiled water. When in a cup it belonged to the owner of the cup, but once on the floor it could not be easily taken back.
Princess Ellen was now a member of the Royal Family of Avalo. The action taken by the Queen of Bozoa can lead to war between the two kingdoms. Especially since Quern Regina was not Princess Ellen's birth mother. If Avalo feels insulted by this action they could ask for compensation. If Bozoa is unwilling, then the war that ended a few months ago will resume.
Queen Regina was angry but even if she wanted to speak, she knew it was better to allow the king to handle it and not get herself in more trouble. She was angry that Ellen had managed to lead into so many problems.