Flame

She was sitting in a clearing and looking at the sky.

As a child, Flamme was the pupil of Serie, who raised her on a whim. Before she became Serie's student, she lived with her parents, at least one of whom was a mage, as they showed her a spell to produce a beautiful field of flowers. This spell is what made her fall in love with magic.
It is implied that Flamme's parents were killed by demons when she was young, hence Serie taking her under her wing.
When Frieren lost her elven village to demons, Flamme took her in and taught her how to fight and use magic for revenge.[9] Flamme empathized with Frieren's hatred of demons and stated that demons had also taken everything from her. She knew Frieren so well that she expected Frieren to one day seek guidance and desire to learn more about humans after making a grave mistake. Flamme set up a grimoire with notes about Aureole—a location Flamme had visited at some point in the past—meant to guide Frieren in the future. These notes were protected by a sapling that Flamme planted and enchanted, which served as the grimoire's protector until Frieren would return one day.
Flamme's dream was to see an era in which anyone could use magic come to pass. This was born out of her genuine love of magic. When Flamme was younger, in human society, all forms of magic were deemed to be demonic techniques, and thus, open research on these techniques was considered taboo.
Flamme was able to influence the Emperor of the largest unified empire on the continent to approve the research of magic country-wide, and she helped establish and educate a new division of Imperial Mages. Flamme was thus responsible for helping to usher in an era in which all of mankind would be able to use magic and acquire the power to oppose the Demon King's army. For this, Flamme is known as the founder of mankind's magic.
Before her death, Flamme taught Frieren a spell to produce a field of flowers, the same one that had made her fall in love with magic.