Killing any one is of course a sin unless it is in a war. You really want to know if women can be given capital punishment and whether a woman can be hit. The answer to both these questions is negative. Women cannot be hit and they cannot be given capital punishment.
Pay respect to womanhood, as they are all born of the family of the
Divine Mother. Punish them not in however mild a manner, whatever the
transgression. Their excellences, not failings, are to be stressed.
Kularnava Tantra, Worship, Readings by M.P. Pandit
Another passage on women is given below.
Then again woman can commit no fault. It is man only that commits
faults. By perpetrating an act of adultery, the man only becomes
stained with guilt. It has been said that the husband is the highest
object with the wife and the highest deity with her. My mother gave up
her sacred person to one that came to her in the form and guise of her
husband. Women can commit no fault. It is man who becomes stained
with fault. Indeed, in consequence of the natural weakness of the sex
as displayed in every act, and their liability to solicitation, women
cannot be regarded as offenders.
Mahabharata Santi Parva Section CCLXVI
There are some stray passages that suggest hitting a woman. However, they can not be accepted as scripture because they do not satisfy the test of reason. Even a Shruti passage is invalid if it does not satisfy the test of reason.
Bhishma said in Mahabharata:
Even the words heard from an ignorant person, if in themselves they be
fraught with sense, come to be regarded as pious and wise. In days of
old, Usanas said unto the Daityas this truth, which should remove all
doubts, that scriptures are no scriptures if they cannot stand the
test of reason.
Mahabharata Shanti Parva Section CXLII
Only passages that speak of love, justice and fairness thus satisfying reason are to be accepted. Those that do not are to be discarded.
The Smritis and the Puranas are productions of men of limited
intelligence and are full of fallacies, errors, the feelings of class
and malice. Only parts of them breathing broadness of spirit and love
are acceptable, the rest are to be rejected. The Upanishads and the
Gita are the true scriptures.
The Complete Works of Swami Vivekananda/Volume 6/Epistles - Second Series/CXXIV