Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Yes, it is permissible to give zakah to needy sisters.
The only recipients that you should not give zakah to are wives, kids and parents. These are your responsibility to care for them even if it will consume all your savings that make you zakah eligible.
Needy brothers, sisters, aunts, uncles or any person can be a recipient of Zakah.
Allah Almighty knows best.