As others said, use a different e-mail for the second account, and be careful about what info you post that might link the two (such as posting the same birth date, or a lot of similar info in the 'About' section for where you live and have lived before or where you worked).

Be careful about posting pictures that might easily be recognized as your male side. I do not believe FB does anything with face recognition to attempt to link accounts proactively, but people who happen across your account certainly could recognize you, and people tagging pictures in either of your two accounts might get recommendations for tagging based on your images in both accounts.

Block your male account and any family member's accounts or people on your male side's Friends list that you wouldn't want to find you. I got outed to my sister because I didn't think to block her FB account. Of course, you can't block everyone but you CAN set your account to only be visible to Friends you have accepted. That means you'll have to be the one doing the Friend requests for anyone that you want to connect with via FB.

If you have ANY friends in common between the two accounts, there is a chance that FB will recommend your new account as 'someone you may know' to friends on your other account. Their algorithm for that seems to work on the basis that a friend of someone you're friends with might be a potential friend for you.

Even with all of that, anyone could report your account as 'fake', and FB will take it down unless you can show real ID, like a drivers license, to verify it is a 'real person's account'.

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There is a way that is 'within the rules' to set up a FB page for a second identity, but it stands a much better chance of being seen by friends of your FB page for your male account. You can create, within your male account, a FB Page for a 'fictional character', such as would be done for an author setting up a page for a character in their stories, for fans to reference. Or such as a band might do, to set up a FB page for fans of a musician or band that is separate from their personal FB page. The problem there is that there is a strong possibility that the page will occasionally get recommended to your male account's Friends as 'someone you may know'.

I did a 'Page' for Ceera as part of my male account, and set no Friends for that page that overlapped my male side. I still got a friend request from one of my male account's Friends. I deleted the Page rather than risk being outed to that friend or any other friends or family.

Since then, I set up a separate account with a different e-mail address, and it's worked fine for years - though it did out me to a few people.