This series is very good, and different than the average villainess isekai. The reason is simple - the past life fills in the missing portions of the villainess. As a villainess with a tragic backstory, she is missing 4 things in my eyes: education, morality, goals, and life experience, of which the past life fills in those gaps, creating a whole person.
Not only that, but the series is well written and the character truly does feel like a combined person, rather than the past life overwriting the current one. This is most obvious in Chapter 10 (spoilers) where the FL has a breakdown due to the OGFL asking the FL's brother if she shouldn't associate with her due to their status differences. She doesn't get angry when her brother agrees she should keep her distance because she has modern values where status isn't relevant, though she does believe that. She gets upset because her mother was driven to her death for this very same reason. This unique combination of both lives reaching the same conclusion really makes the writing special. Her history, her mother's history, the plot, her past life - all of them are relevant pieces of the human that the MC is.
We also see this in other aspects - why does she befriend the OGFL? It's to avoid flags. It's because she likes the character. It's because she has a similar history (mother also died 7 months ago). It's because she's a good person and friend. Both "characters" inside her again reach the same conclusion.