Sorry I don't have info on other sites, but I do know how you feel. I am in my 50s, but I won't share my site name with the family. So far only my older sister knows about my Asperger's, but she figured it out on her own after coming across info on it. She does know about this site, but not my site name. I need a place to post and vent, including about family matters. I don't give out family names or addresses, including my own, so that keeps their and my privacy protected. At the same time, I do sometimes need to discuss stuff that might upset them, so I am keeping my site name off the family radar. I may eventually tell the others about my Asperger's, but I have not decided yet.
If your mom doesn't know your site name, it should be okay to let her know about this site. It can be very helpful to her. Also, you can always check for other sites yourself by doing a search for them.
Anyhow, glad you like WP! I certainly do! 
_________________
If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau