There is this girl who finds a scientist who has created a machine. I can't recall if he clones her or if he makes her look into a mirror but she ends up either cloned or in the past and the other self lives in the present or something.

The main plot is to prevent a sister's death in the past but the sister accepts her fate.

I am checking the time travel tag atm but if anyone has any idea / can verify I have details correct, please say something.

Its a manga btw.

https://www.mangaupdates.com/series.html?id=50669

Found it, please lock this thread.