It depends on what the name is trying to say. I think what you mean here is 'Women's Shirts'.. the plural of 'woman' - women, then the possessive apostrophe 's' (which you can't have in a domain name) - meaning suitable for women, and then the plural of 'shirt' - shirts.
So 'Women's Shirts'
(or for a domain 'WomensShirts' - without the apostrophe for the possessive 's').
A bit better than 'Woman Shirt' would be 'Women's shirt', but this is singular (meaning one shirt).
'Woman Shirt' as a meaning for a 'shirt for women' is not really correct in English.
I hope all that makes sense