Scarlett

Scarlet was the Muggle friend of Penny Haywood, who was killed by a werewolf in the summer of 1986.

Biography
Scarlet was presumably born around the same time Penny Haywood was born, in the late 1960s and early 1970s, and was raised in the Muggle world. Every summer, Scarlet and her family would holiday in the countryside, where they befriended Penny and her family.

In the summer of 1986, Scarlet and Penny snuck out of house at night at full-moon. They found a werewolf which fascinated Scarlet. Scarlet followed it while Penny followed them with her wand ready. Eventually, the werewolf noticed it was being followed and turned around. It killed Scarlet before Penny had time to react.

Penny later blamed herself for Scarlet's death and tried to drink the Forgetfulness Potion. From then on, Penny's boggart became the werewolf.