Will a sister who adheres to the hijab and niqab be held accountable for not advising her older sisters who do not observe the Islamic dress code, especially since they are aware of the obligation of the khimar and reject advice, and due to the family's anger if she advises them?

If the sisters go out displaying their adornments, they must be advised with wisdom and good counsel. If they do not respond, then there is no sin upon you after offering the advice.

However, if they do not cover their faces while wearing the legal hijab, this matter is a point of disagreement among scholars, and it is not obligatory to condemn them for it, unless they go out with their faces uncovered and adorned, in which case they should be gently and wisely advised against it.