As soon as the battle begins, run up to her and use a crush weapon or fire spells. Remember to use one that's far below your magic level because her spells can lower stats, as well as reducing a player's special attack bar to 0, so stat restore potions are highly recommended. While fighting, she will freeze the player and teleport away from the player, so patience (as well as a one click teleport) is advised.
She can be fought in the Nightmare Zone after the quest is complete. However, her Nightmare Zone version is currently bugged and will freeze players rapidly and repeatedly, reducing their stats to 1.If you fight her in Nightmare Zone, turn on protect from magic and leave it on. Karamel will teleport next to you and start using melee until protect from magic is turned off.
If you are a low level player, DO NOT underestimate her magic attacks, as they can hit rapid 7s. The best way to avoid damage is to run up in front of her, so she can use her very inaccurate melee attack as well.