Can you reduce the number of female clients in settings?
No, unfortunately,
Option 1, You can also go into the savegame and delete the female or male tourists/citizens. Load the game and let your base repopulate. You may need to do this a few times to get the ratio you. The good news, it will get faster as you progressively do this.
Option 2, depending your how fast your computer is, you can just enslave the tourists/citizen, then sell them. And hope your base repopulates with the preferred gender.
Option 3, edit your save game first, then trim as you play with option 2
Also, Tourists come and come go I believe, so you may never get what you would like 100% of the time.