Tina Shepard was born the daughter of John and Amanda Shepard. They lived on a house on the shores of Crystal Lake. Although John Shepard loved Tina, he was also an easily enraged alcoholic who frequently beat his wife. During one particularly violent spat, an angry Tina ran away from the house and got in a boat. Fearing for her safety, John ran out on the docks and attempted to apologize to Tina and get her to come ashore, but she responded by saying she wished he was dead, and began envisioning him dead in her mind. Unfortunately for both of them, Tina possessed immense telekinetic abilities that could only come out during times of extreme anger or stress. She caused the dock to collapse, drowning her father. Tina was traumatized.
Amanda Shepard tried to get her daughter help by sending her to the famous psychiatrist Richard Crews, who began living with them when he realized that he could exploit Tina's powers for personal gain, and began gaslighting her in order to make her mad enough for her powers to come out. The "family" came to Crystal Lake many years later. Crews claimed this was so Tina could deal with her trauma, but he actually wanted the painful memories of the area to jar her abilities.
Sure enough, Crew's increasingly domineering ways, the weak-willed reactions from her mother, as well as the cruel taunts of a local rich girl named Melissa (as well as Melissa's circle of friends) caused Tina to exhibit her powers. Only a local boy named Nick who had fallen in love with Tina and a shy girl named Maddy showed her any kindness, and Tina rejected both of them. Tina likely would have killed all of them in a fit of rage if it wasn't for what happened next.
Tina attempted to use her powers to resurrect her father's body (which had never been found), but instead awakened a dormant Jason Voorhees, who proceeded to slaughter everyone at the Lake, including Crews, Maddy, Melissa and her mother. Falling in love with Nick, and finally accepting herself for what she was, possibly because she saw in Jason the monster she could easily become, Tina gained control over her powers enough to battle the brute. She gave Jason the beating of his un-life until she was saved by a mysterious figure that dragged Jason down to the bottom of the lake. To all appearances, this being was John Shepard. Whether this truly was him, or simply a delusion of a weary Tina, is unknown.
Tina appears in Wildstorm's Freddy Vs Jason Vs Ash: The Nightmare Warriors. She has increased control of her abilities, and formed a special bond with fellow psychic and Jason-survivor Rennie Wickham.