I see.

So from what I understand here is a quick point form breakdown of your story so far:

MC – candle maker

flaw – naive?

inciting incident – twin being kidnapped

external goal – save MCs twin

internal goal – grow up? become mature? take responsibility?

antagonist – sorcerer

obstacle – monsters

ally/possible love interest/possible mentor – knight

main action – fight monsters and sorcerer

Making the brother a twin raises the stakes even higher really good addition.

Has the making of a well structure story and it sounds interesting as a fantasy adventure I would go watch this movie.

I suggest redrafting the logline to include: inciting incident, MC+description, external goal, main action, antagonist, obstacle and (if word count permits) ally/possible love interest/possible mentor.

I don’t think this logline needs her magic powers mentioned nor the specifics of the knight, his abilities, personality and dragon friends, knight is enough to describe his character in the log line.

i.e:
After her twin is kidnapped by an evil sorcerer a candle maker with the help of a knight must fight the monsters in the dark realm to reach the sorcerer and save the last remaining member of her family.

The character description in this logline jumps out and not in a good way. Currently there are three things the MC is: young, a candle maker and has magic powers. Economy in words adds power to a log line so better to use a shorter more potent description for the MC preferably a description that will make it seam like the MC will have a hard time achieving her goal.

The ally being aloof reads more like a Don Quixote type character than a monster fighting hero, what will be his function in the story once they enter the dark realm? Also what is a dragon night? Is he a dragon or a night that fights dragons?
Perhaps better to describe him in a way that clarifies his use to the MC.

Lastly there appears to be two separate parts to the story in the one log line; first is about the MC fighting monsters in the dark realm the second about saving her brother.

I understand that the second part of the logline is there to put pressure on the first but it doesn’t read this way. For the causality between the two parts of the log line to be clear define the inciting incident as the kidnap of the brother by the sorcerer first then describe her action in fighting to save him.

example:
After an evil sorcerer kidnaps her brother a young candle maker hires a retired dragon slayer to help her rescue her brother and save the land from the sorcerer.

Hope this helps.