Fantasy manhwa where the female lead is poisoned when she becomes the empress

Question

Manhwa where in the beginning, the female lead is destined to marry the future emperor. When their coronation comes, she’s extremely frail and dies; she’s replaced by another woman and her husband does nothing to save her. Turns out she’s been poisoned and dies after being abandoned, before waking up and finding out she travelled back in time.

The protagonist has blonde hair and blonde eyelashes.

It's not A Marriage Alliance for Revenge. The female lead doesn't have white hair. I don't remember the hair color of the male lead. She's betrayed by what I think was her cousin, who has short brown hair and purple eyes.

Answer 1

This is There's No Use Hanging On. It is licensed by TappyToon.

Kaira willingly risked her life to make her beloved Prince Reagan emperor. But when the man she sacrificed it all for crowns her cousin as empress instead of her, she loses the will to live. It’s only when she’s finally succumbed to a lethal dose of poison that she’s met with the tears of a heartbroken Prince Faylon, and she realizes her love was wasted on the wrong person.

Synopsis covers much of the question. The protagonist helped the upcoming emperor become emperor, and on his coronation he announces that her cousin will be his empress. She appears at the bottom of the 2nd image below, and has brown hair and purple eyes. The protagonist has blonde hair and eyelashes.

After dying to the poison and being cast out, she regresses and plots to make another man emperor instead.

Found by searching mangaupdates for the tags Betrayal and Time Rewind, and searching for blondes on the covers.

Answer 2

Could it be A Marriage Alliance for Revenge by Heesa Yun and Emma as per Manhwa that starts with the emperor poisoning the empress with their child in her stomach?

Empress Olivia knows happiness is the last thing she deserves, but when she finally becomes pregnant with the emperor's child, she thinks things might finally be taking a turn for the better. Alas, Olivia realizes how naive she was when her husband poisons her tea, killing both her and their unborn child. When Olivia opens her eyes again in the body of an unknown woman in the slums, she vows to take vengeance against the emperor. To do so, she forms a marriage alliance with her former fiancé, Duke Lucas Viterpan, the true heir to the empire who was deposed in a coup. Will this man and woman who had everything taken from them succeed in getting revenge?

The eyelashes look a little darker, but it is otherwise a match.