I was never legally married to her father but we lived together for 20 years
We have been separated for 2 years
As long as the benefits are ONLY for your US citizen daughter .. it won't impact on you.
But, you didn't tell us how you think you qualify for US residence .. .thus, you should meet with an attorney.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.