my sister has asked me to send a box to her in which there are things that she will be using for both halal and haram causes,in this case is it permissible for me to send her that box? note that she has asked me to send someone else to give her that box.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

As long as you know that your sister will use that box to keep what is forbidden, you should not help her obtain it, either by sending it to her or otherwise.

The jurists discussed in their books the ruling on selling items that may be used for permissible and impermissible purposes and stated that it is not forbidden for a Muslim to sell such items unless the seller knows or predominantly believes that it is most likely that the buyer will use them for a forbidden purpose (in a sinful way). In this case, it is forbidden to sell such items to such buyer. Allah, The Exalted, Says (what means): {And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allah; indeed, Allah is severe in penalty.} [Quran 5:2]

This applies to the case you give her the box yourself or send it to her with someone else.

Allah knows best.