I need to know more

Same. I dont understand. Maybe the original girl is infertile and they need an heir? I'm just guessing ╮(￣▽￣)╭

But then in the prologue the og girl said that when she gives birth to a new child she'll dispose of elena's baby. Honestly, i dont understand either why they want elena so bad

Maybe she loocked like viscounts daughter? How could she have takens over her life otherwise? ╮(￣▽￣)╭

i think what they meant is that why did they need a look alike (aka Elena) so badly ?
If the villain was already a candidate, couldn't she just be the queen instead of going through the process of a swap?

I saw a comment somewhere with a theory I liked a while ago (can't rmbr where or by who, so sorry about that!). Basically, since the path towards power / being empress is hard and dangerous, I'm pretty sure they want Veronica to remain in hiding and for Elena to take her place so that Elena gets dealt with all the hardships and danger while Veronica rests lazily and takes her place once the hard stuff is over, and eliminating Elena so that the takeover is easier.

Some spoilers about 1st life that I've read from others. P.S. This might be long.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
So the prince was married to the crown princess Cecilia by political marriage so no romantic feelings between them. Then the emperor (crown prince's father) health is deteriorating so they needed a concubine. The crown prince refused at first but due to pressure of nobles and even Cecilia's father, he eventually agreed. There were 2 candidates for concubines which is veronica and another one, but eventually veronica was the chosen concubine. So Cecilia will become the Empress, and Veronica will be the Queen. Veronica was then poisoned ( I dont know why or who did it), but there was no antidote to it, the only solution for it, was to let the poison pass throughout her coma. So they needed a substitute for Veronica, which was Elena. But then Elena was a very great concubine (in affairs and everything), so they continued Elena pretending as Veronica. Eventually the prince fell in love with the new Veronica (which is Elena), thats why they had a baby. But in order to protect new veronica (Elena), the prince was cold to her in front of the nobles, but behind the nobles sight he loved her so much. He did this to protect the baby and new veronica (Elena), to the point that he built a secret place in the palace for her. Now, the only way new veronica(elena) can survive all these events after, is to escape the palace unnoticed. The prince then was worked so hard to prepare and plan for her escape. Eventually the baby was born. Throughout all these, New Veronica (Elena) didnt understand why he was cold towards her and the baby. She was hurt so much from the prince's action. He wanted to confess to her, but then it was too late already. The real veronica recovered and now replaced Elena. Real Veronica now imprisoned Elena in the palace for some time and was then killed. When he heard the news, he went to the prison and hugged Elena's body and kept saying I'm sorry. Also, throughout the story, at first the prince didnt know that the real veronica was replaced. He just then noticed slowly that the personality of new veronica (Elena) was changed and that he's already falling in love with the new veronica (Elena). And at the end of first timeline, when asked about the events that Elena encountered, the family of real veronica used the excuse of amnesia. I dont know about the second life though. All I know in second life is that the prince didnt marry Cecilia and reserved the slot of crown princess for Elena.