My mom is gay. And I know it shouldn't bother me to come out to her. But I'm afraid that she'll have that " I knew it " attitude. And such.
If she knew it, what can you do about that? If she didn't know, well now she will. You can't change the past, and the future has yet to come. Stay in the present and ask yourself, "Are my fears really justified? Is there any real benefit waiting to come out?" Ultimately, I think most parents, especially moms, know their kids may not be straight, but they may not realize it at first due to cultural/religious reasons.