Queen Regent is the woman who takes place of the Queen but is not the coronated Queen. If it was medieval times it would have been patriarchal and so while she was Queen for now, she would have to step down when the King gets married, correct? She is not the full Queen, she is stepping in until he gets a wife.

Furthermore, it's why she did get the throne. And she has serious depression and anxiety issues. She knows she is not a good fit for the throne and she wants the kingdom to have a monarchy who can actually function in society, unlike her. But I did make her Queen(and am realizing this minute I forgot to change that in the CS).