是这个女士的，用英文怎么说？

it's the woman's
或者:
it's the madam's
it's the young lady's

It is hers.
如果说：It is the lady's.就太死板了，可以根据语境修改．

It is hers.

oh,the lady owns it.

3楼正解.

The madam is its owner.