Forum:Marceline's healing power's make no sense

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So i'm guessing that her being half vampire gave her the ability to survive in sunlight before she became full vampire, but why wasn't/ isn't she able to survive in sunlight? The vampire she stole her healing powers from could, and the fact that the pain of being in the sunlight didn't wake her up says a lot. Technically she never even died, she got absorbed while still alive. So the vampire she stole her problems from can survive in sunlight while ALIVE but she can't even swipe an umbrella within arm distance and endure a few seconds of pain?