I forgot the title. AGHHHHH

FL: younger than ML, brown hair, green eyes
ML: older, a Duke
They meet when FL is a child and ML is a teenager
ML leaves for war
FL says she wants to marry him; he tells her to grow “as tall as a tree”
Adult FL works with plants/botany
She creates something forbidden and is executed
ML grieves and turns back time
FL returns without remembering the previous timeline
They eventually marry