Heather Hernandez is a supporting protagonist in Totally Killer.
Biography[]
Heather Hernandez was a high school student and a member of "the Mollys", a gang of mean girls that consisted of her, Tiffany Clark, Marisa Song and Pam Miller. At some point, Marisa and her friends had been involved in the death of a student they called "Fat Trish", who was rumored to have had sex with their PE teacher, Coach Zane. The Mollys thus invited Trish to a sleepover at Tiffany's house and got her heavily drunk in an attempt to make her "confess". However, Trish got upset and, after locking herself in Tiffany's room to cry, attempted to drive home whilst still intoxicated, leading to a fatal car crash.
In the original timeline of events, Heather was murdered on the night of October 31, 1987 -- her 16th birthday -- whilst hanging out in the parking lot of a local carnival. She was stabbed 16 times by a masked Doug Summers, who was looking for revenge for the death of Trish, his former girlfriend. Tiffany met the same fate four days prior during her 16th birthday, as did Marisa two days prior.
However, after Pam's future daughter Jamie accidentally time travels back in time to October 27, 1987 from 2023, she decides to register herself into the high school, where she meets the Mollys during gym class and learns of their plans to throw a party at Tiffany's house for her 16th birthday, which is where Tiffany will be murdered. Jamie infiltrates the party and tries to stop the murder, but is too late.
Death[]

Heather's body
Following Tiffany's death, Jamie manages to convince the rest of the girls that she can tell the future, and warns them to stay out of town for the weekend. However, this backfires since Jamie and the girls wind up at the exact cabin where Marisa was killed in the original timeline. That night, the Sweet 16 Killer arrives, but decides to go for Heather instead of Marisa. Despite the rest of the friend group trying to fight back, the killer succeeds in stabbing Heather 16 times, killing her.

James gave her death the Dull Machete because we had already seen the Sweet 16 stabs a few times already.