JSFiddle - React, Tailwind, and code Playground

HTML

<div class="flex">
        <div class="other-item">
        100px tall
        </div>
        <div class="flex-item">
            <div class="element">
                Should also be 100px tall because total min-height is 200px<br />
                The orange element should be as tall as the blue element
            </div>
        </div>
  </div>

CSS

.flex {
    display: flex;
    flex-direction: column;
    min-height: 200px;
}
.flex-item {
    flex-grow: 1;
    background-color: steelblue;
}
.element {
    height: 100%;
    background-color: orange;
    min-height: inherit;
}
.other-item {
  background-color: peachpuff;
  height: 100px;
}