"Oh sweetie, love that you beg even when I'm feasting." She pulled away and grabbed something from her bag.  Her eyes darted about as she pulled out a cigarette. "You intrigue me, and we seem to be alone.  So I will humor you."  She lit up and took a long drag.   Her eyes closed with pleasure.
"Hmm, perhaps we can make a deal?"  I could barely say the words.  My neck felt warm, and wet trickled down onto my shoulder. I lay on my back against the soft grass.  Her legs straddled my hips.  Dizziness made my brain fuzzy.  "I'm quite... resourceful."
She smiled.  Her eyes gleamed darkly.  Red liquid stained her chin and the front of her chest.  Black matted hair clung to her damp face.  "I doubt you can offer me anything of value."  She exhaled a cloud of smoke and pushed the butt into the ground.  "Normally I don't socialize, but you seem interesting."  She leaned forward and caressed my cheek with a ragged dirty fingernail.  "I don't get the chance to chat much.  Go on..."
I gulped.  My mind went blank.  Was it the blood loss or did she have some strange affect on me?  I spit out something stupid, "How old are you?"
She raised her eyebrows and laughed.  "A gentleman never asks a lady her age!"  She leaned back and put her hands on her thighs.  "But I'll indulge you.  I'm 653 years old."  She waited for my reaction.
"And when did you become a... vampire?"
"Well, darlin', let's just say I'm eternally 29."  
"Yes.  You look quite young and attractive."  I hoped the compliment would keep her talking.
She cocked her head.  "Oh, you are desperate to think that will change anything. Silly boy."  Her eyes glowed in the darkness.  "Yes, only a silly boy would walk alone at night in the park.  Haven't you read the papers?  I was happy to find anyone after all recent fuss."
"Yes, I've heard there was a killer on the loose.  But I carried protection."
She picked up a cylinder and dangled it in front of my face.  "Oh, you think mace would do anything to someone like me?"  She snorted.   "Seriously, this stuff is more annoying than harmful.  Now where were we?"  She licked her lips.  "I'm still hungry."
"Wait, wait... I thought we could talk some more."
She paused as she bent down close to my skin.  Her tongue flicked my neck.  "Hmmm, ok.  Talk to me.  Tell me why I shouldn't kill you right now."  Her legs tightened about me as she played with my hair.
I looked up into the sky.  Grey clouds drifted overhead, but I could make out a brightness behind them.  The full moon would appear soon. 
"I could be your servant.  Don't vampires needs someone to protect them during the day?"
She hovered close to my face.  Her cold breath stunk of moldy death.  "I think you've watched too many movies.  But I admire your will to survive.  Most meals give up and die."
The clouds parted, and the moon made an appearance.  I could feel the strength returning to my muscles.  My heart pumped harder.  Energy surged into my being.  My senses grew sharper.  
"I can tell you are lonely..." I tried to sound sympathetic.  "And I could take care of... other needs."  This sounded lame even to me, but stalling was critical.
Her body stiffened.  A hiss escaped near my ear. "Don't flatter yourself.  I only need blood.  I don't need anything else.  You're a pathetic helpless human, and you're boring me now."  Her nails dug into my left shoulder, and her right hand yanked my hair hard to pull my head back.  Her long sharp fangs glistened in the shadows. 
The moon's magic invaded my body.  Waves of adrenaline pumped through me as I morphed into a stronger being.  Even as she bit into my neck, I knew it wouldn't matter.  The change made me stronger.  It protected me against her attack.
I gripped her arms and flung her off my body.  Her teeth tore out a chunk of flesh, but I didn't care.  The wound would heal.  She was nothing, a lesser being who preyed on those she thought were powerless to her abilities.  
I felt my nose and mouth expand to shape itself into a wolf's snout.  My teeth grew large and pointed.  Hair sprouted on my arms, legs, torso, head and neck.  My body transfigured into something grotesque and animal.  For once, I felt exhilarated with my new form. 
She gasped in surprise.  No doubt this was the first and last time she would see a werewolf.  I gleefully howled and dug into her chest to rip out her beating heart.  My hand squeezed and the pulp oozed through my fingers.  She would die - after all, wasn't this the best way to kill a vampire?  Her body jerked and lay still.  To be sure of her death, I ripped off her head.  
After that, all reason left me.  The wolf inside took over fully.  I knew no more until the dawn.  I woke up to find myself naked and covered in blood, lying on the ground by some bushes.  Well, that was nothing new.  It was a frequent enough occurrence.  Only this time I knew I had killed someone who deserved it.  
My lover died a week ago.   My soul mate, another werewolf, was taken from me.  My heart and mind became consumed with one purpose: Destroy her vampire killer.
So I waited until the moon was full, and I walked in the same park knowing I would be a easy target.  No one else would be around.  People stayed indoors and safe.  And the savage beast could take revenge without harming an innocent.  
I retreated from the daylight before I would be seen.   For once, I didn't worry about the evidence of my slaughter.  The sun would burn the vampire into ashes if the lore held true.
Word count = 997.  
I was inspired by this idea:  A werewolf loses his lover.  He and she are bound together as lovers.  Finding another werewolf lover would be next to impossible.  If one were to die, the other would live unhappily ever after.  So the story then became how would she have died and if a vampire did how could the werewolf defeat the vampire in his human form.  Answer: Wait until the moon is full.  But there's only a slim chance to pull this off during transformation - when he is both human and wolf.