Hi Monica,
Because I do not know the trigger, I interpret this dream based on the meanings of the symbols only. It appears that you and whoever your sister presents (a church congregation, your real sister or a spiritual sister (Christian), or a group of women who are Christians) currently experience difficult situations or a negative situation, that is why you are walking in the dark. However, you have the word of God in your hearts, and you are led by his word (lamp above always there).
The Bible in your hand may speak of you arranging and organizing things regarding the situation, according to the word of God (See the meaning of hand). The fact that you are about to proceed to or access an area where there is no light speaks of the situation deteriorating or more demonic influences and activities taking place.
Two things are obvious at this moment: Whoever is represented by your sister will in a sense be dismayed and lose faith a bit but you are stepping in and comforting them or her. YOur exhortation will be necessary to help them through this situation. The praise and worship are probably literal and will be necessary in and for the situation but it also speaks of pointing her eyes or their eyes and attention onto God and what He has done. Focussing on God will help them to stand firm and to be victorious in this situation.