I dont think she is trash in the first life it was the story of a book which means they were only book characters without choices themselves in the second life as we saw she fell in love with noah because aerinda choose to live the same life as in the book so nothing cause a change except in the end when aerinda was executed she didn't blame serena cause she knew that she wasn't at fault and was a kind soul because of those emotions serena experienced a change and asked luke for the time to turn back when they turned time back she saw that aerinda was staying away out of fear and she choose to marry noah in hopes that he would leave aerinda alone even tho serena didn't feel that way toward noah when she saw that didn't work she asked luke to turn time back again this time in exchange for her magical power to be cut in half then she met aerinda first and that caused a change her and luke getting close to aerinda so i dont think she isnt trash because she got close first if thats all you took from the story i think you should read it again
Serena is a whole weirdo for marrying a guy already married. The only reason she's not trash as the prince this reincarnation is because she met the MC first. The mc being fine with this because she's pretty is also weirdly.