If you want to get it really right, then you need to say:

To one woman: as-salāmu ʻalayki (or ʻalayk)

To two women: as-salāmu ʻalaykumā

To three or more women: as-salāmu ʻalaykunna (or ʻalaykunn)

To a mixed group (men and women): as-salāmu ʻalaykum

If you want to get it really right, then you need to say:

• To one woman: as-salāmu ʻalayki (or ʻalayk)
• To two women: as-salāmu ʻalaykumā
• To three or more women: as-salāmu ʻalaykunna (or ʻalaykunn)
• To a mixed group (men and women): as-salāmu ʻalaykum

If you want to get it really right, then you need to say:

to one woman: as-salāmu ʻalayki (or ʻalayk)

to two women: as-salāmu ʻalaykumā

to three or more women: as-salāmu ʻalaykunna (or ʻalaykunn)

to a mixed group (men and women): as-salāmu ʻalaykum

If you want to get it really right, then you need to say:

To one woman: as-salāmu ʻalayki (or ʻalayk)

To two women: as-salāmu ʻalaykumā

To three or more women: as-salāmu ʻalaykunna (or ʻalaykunn)

To a mixed group (men and women): as-salāmu ʻalaykum