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Actually you aren't trying to beat Sylvie, you are supposed to defeat the NM Burgeoning Flames that spawns as a result of the Quest that you trigger with the NPC Sylvie. I will paste the walk thru page for the Quest named Elementary, My Dear Sylvie below and will also paste a link for the NM Burgeoning Flames. There is a testimonial page at the bottom of the Burgeoning Flames page where other players have given accounts of how they approached the fight that may help you.  

I revamped my last answer after dgoing some research.  The input by Blue Donkey Kong I would say is solid.  He is a daily poster on the site under multiple categories.  The 2nd poster gives very detailed advice, which I always like to see.  The sad fact of the matter is that not a lot of info has been put in ANY database regarding the Burgeoning Flames.  I went to Google and got only 4 hits. Sorry.  If you have info or strategy to add after your fight, PLEASE create an account and add your testimonial to help other players in the future.  Skyfiredancer (talk) 05:16, May 24, 2015 (UTC),_My_Dear_Sylvie