Ginger Snaps 2: Unleashed

After the events of the first film, Brigitte Fitzgerald uses monkshood extract to fight the effects of the lycanthropy that transformed her sister into a werewolf. Brigitte shaves her body, cuts her arm with a scalpel, and logs the data about her healing ability. Ginger, her dead sister, appears as an apparition and warns her that monkshood is only a treatment, not a cure. After Brigitte injects a second dose of monkshood, she senses the presence of a male werewolf that has been stalking her. She quickly packs and open the door, only to find Jeremy, a flirtatious librarian who has brought to her several books she attempted to check out earlier. The second injection causes toxic shock, and Jeremy attempts to bring her to the hospital; however, the male werewolf mauls him to death. Brigitte stumbles down the street and collapses in the snow.
Brigitte wakes in a rehab clinic, from which she unsuccessfully attempts to escape. She pleads to be released, but the clinic's director Alice refuses. However, Brigitte palms a piece of glass to measure her healing rate. Tyler, a worker at the clinic, offers to trade monkshood for sexual favors, which she declines. As her healing rate accelerates, so does her rate of transformation. Ginger continues to appear, taunting Brigitte as she experiences growing cravings for sex and murder, as did Ginger previously. During a group therapy session, Brigitte fantasizes about being instructed to lie on the floor and masturbate; a vision of Ginger jolts her back to reality, and her palm is revealed to be covered in hair. Later, depressed, she holds the shard of glass to her throat in front of a mirror, but she does not kill herself.
While at the clinic, a girl named Ghost â the granddaughter of Barbara, a severe burn victim at the hospital â shadows Brigitte and realizes her secret. Ghost slips Brigitte a werewolf comic book and begins to question her about lycanthropy. When Ghost notices that Brigitte's ears have become pointed, Brigitte cuts off the tips. Ghost attempts to slip Brigitte more monkshood, but Tyler prevents it. In despair at her rate of transformation, Brigitte allows Tyler to inject her. After the male werewolf tracks Brigitte to the clinic and kills a dog that Ghost had cared for, she and Ghost plan their escape. They crawl through air vents to reach the basement, where they encounter Beth-Ann, a patient who traded Tyler sex for drugs, shortly before the male werewolf kills and drags her away. While fleeing the werewolf through the old hospital's crematorium, Brigitte is mauled; her leg being broken and a piece of tile punctures her chest. Her wounds heal quickly as she and Ghost escape through the furnace, dousing their pursuer in gasoline and setting it on fire.
Ghost drives them to Barbara's house and explains that Barbara fell asleep with her bedtime cigarette. After they sleep and Brigitte almost gives in to her urges, nearly eating a deer killed by a boobytrap Ghost had set for the Werewolf, they arrange a meeting at a gas station with Tyler to procure more monkshood. Brigitte wanders into the gas station looking for Tyler, where she discovers the attendant has been slain. She quickly returns to the car and the three of them return Barbara's house to inject the monkshoodâwhich Brigitte's body rejects. Worried that Brigitte is OD'ing, Tyler calls Alice. Ghost tricks Brigitte into thinking that Tyler abused her, and Brigitte locks Tyler outside, where the werewolf kills him. They then go about setting up a mattress with spikes below the basement trapdoor so that Brigitte can kill the werewolf when it shows. When Alice arrives, Ghost mistakes her for the werewolf, and attacks her with Barbara's hunting rifle. Meanwhile, Brigitte finds evidence that Barbara is not a smoker, so she aggressively pins Ghost against the wall and argues with her; she realizes that Tyler did not abuse Ghost, and Ghost herself burnt Barbara.
Alice attempts to take Ghost with her, but retreats to the attic once the werewolf breaks in through a window. Brigitte, whose transformation is almost complete, lures the werewolf into a room. Brigitte stabs him while Ghost distracts the werewolf. The werewolf bites Brigitte, and, as they struggle, they both fall into the basement, where the werewolf is impaled on the trapped mattress. Ghost hits Alice with a hammer, and a weakened but not yet fully transformed Brigitte begins to climb the ladder back up into the house. Instead of helping or killing her with the rifle, Ghost pushes Brigitte back down and locks the basement. The next scene is some time later, the house repaired as Ghost illustrates a comic book that depicts herself as a powerful warrior with a werewolf pet; Ghost narrates that Brigitte is getting stronger and is waiting to be unleashed on her enemies. As the film ends, Ghost prepares to welcome Barbara home.

Question: What does Brigitte palm to measure her healing rate?
Answer: A piece of glass