Im looking for something like this:
There is a black haired girl who gets power from a flower, and maybe she has red eyes, bit i'm not sure...
Which manga is this😕
Thank you!

Is it Sankarea? She's a zombie girl that has to eat flowers to live.

yeah thats what im also thinking of, shes a girl who died accidentally but luckily drank a reviving potion before the incident hopping that she'll die because of the ingredients used in making it that was poisonous.