
From what I know, the MC is a queen meaning shes a rank lower than the empress. When the emperor said he'd marry the MC as a queen, you can see how furious her father was, this is because a queen is like a spare to an empress. She can never become empress unless the empress the emperor crowned dies. The Male Lead probably married the MC to shut his cabinet about an heir problem, however, he was unwilling then to marry her as an empress. Thus he just made her queen. Hope this helps.

She is the empress consort not the empress reagent... The empress consort is similar to queen consort (if she get married to a king she will get this title).
But in this case.. she got to married to the emperor... so she was know as the empress consort.
Gahh!! now I'm confuse with my own words. I hope that you can understand what I'm trying to say here... sorry for my bad English lolヾ(❀╹◡╹)ノ~
http://www.mangago.zone/read-manga/i_don_t_want_to_be_empress/
Same? Yeah... the only difference about these two is... this one got update until ch10 while the other one only until ch5... welppp... what ever... I will still read these two manhwas (⌒▽⌒)