The idea is that Chun Yuan doesn’t look like Zhen Huan, but instead looks very much like An Lingrong, right?
As for her appearance, this is my own headcanon: Empress Chun Yuan is a petite, unassuming beauty like An Lingrong. In a harem full of beauties, she wouldn’t stand out. But in Yin Zhen’s eyes, she was the most beautiful woman in the world. Yin Zhen praised her so often that, after all, she was just one of the women in his household, and the only people she’d meet at social events were nobles. Others might have thought her pretty, but not the most beautiful woman in the world. Still, her husband kept praising her, and after she’d been dead for countless years, her reputation as an unparalleled beauty gradually spread.
That’s more or less the idea.
In a sense, the one who deserved to die was Fat Ju. But that’s how the harem works: succeeding once doesn’t mean you’ll succeed every time.