The Breed

Some Youngsters , a pack of Dogs, lots of blood and Gore.Well that's the short version, here's a little more detail.A group of teenagers visit an island where there uncle, an animal rights activist, used to live before he died and left them his house. The bookish older brother has agreed to come along with his younger brother despite having term medical papers to finish. They tell the others the site used to have a dog combat training site but the dogs were destroyed because of a rabies outbreak.The kids all kick back having a good time and while they are outside they see a little puppy and fuss over it and take it in the house. That night a dog comes looking for the puppy and ends up biting Sara. They chase the dog off and Sara decides to stay on the island instead of going to the mainland because she is advised that she has up to a week to get a rabies shot. That night she comes on to one of the guys but gets a little violent while kissing him and he backs off.Next day the guys go into the wood to see if they can "find something to shoot" with the bow and arrows that they have. While they are there they see a guy who has been attacked by the dogs who just has time to tell them that the dogs don't want them there before the dogs finish him off.They all decide to escape on the boat plane they flew in on but the dogs have chewed through the tether and are sitting on the wings waiting for them. While they are retreating they youngest brother accidentally shoots Niki through the leg while trying to shoot a dog that is attacking her.They decide to try and get the car from the garage but they have to cross to do that. Despite her injury Niki does this but can't get the car to start and narrowly escapes another attack from the dogs.All back in the house they try to settle back and relax for a while when the black guy has to go to the basement to fix the fuse when it blows only to find the dogs have a way in through the basement and they tear his throat out.The dogs chase them through the house and they all end up in the attic where they find some papers that suggest the uncle may have been involved with the dogs being trained at the combat site. They know they have to escape and decide to go across the island to the centre. The guys manage to get the car going but not before Sara sacrifices herself to save them by keeping eye contact with the dog to hold it still long enough to let the others get out, but the dog attacks her and she falls to her death.At the centre they discover that the dogs have genetically engineered and have gone out of control. They try to radio for help but cannot. Niki notices a cable is detached from the aerial and the guys try to fix it but get attacked by the dogs. Meanwhile the dogs corner Niki but she escapes with the aid of a leaking gas bottle and a fire. The guys are fighting dogs outside when she rolls up in the car and asks if they need a ride.They drive across the island and drive the car into the sea and make their way to a nearby yacht. Once on board they agree that they need to go for help but need a rest first. They open the door to go into a cabin and the last thing we see is a dogs fangs launching towards them gnashing and snarling...

Question: Why did Sarah stay on the island?