I found using ranged attacks worked really well against her. Make sure آپ bring a mage (use group heal every time she throws a آگ کے, آگ ball at you, if آپ can't make sure آپ have lots of health poultices) and some archers. Bring one tank with آپ to attack flemeth in close range. They'll probably die, but it keeps her distracted from attacking the raged attackers for a while. Acid flasks and different bombs can be quite useful as well^^
I'm sorry I that wasn't much help... that's how I defeated her.
Having finished the game a multitude of times, I've tried all different ways with this one. It's basically an easier version of the archdemon - but judging سے طرف کی the question, آپ haven't gotten that far yet. The best way I found was to make sure آپ have Wynne (circle of magi 'broken circle' quest - can recruit her), یا at least the 'spirit healer' specialisation for a mage. Then make sure he / she has revive, یا at least group heal leveled to their character. If آپ keep the healer selected and out of the way, آپ can keep an eye on the rest of your party while they tear seven shades of shit out Flemeth, while آپ sit back and heal when necessary. I found this way rather quick, as well. Hope this helped! :)