T.O.
I see both sides. I know she wants to be part of your life, and with all the kids gone she must be lonely.
However, you have a right to privacy too. I am not on my daughter's pages, but they're teens and I could get to them if I wanted to... I do periodic checks. But I do love seeing their blogs, their comments and stuff.
I'd say you can ask your mom to visit, but take her off as a friend. And because of employment issues, I wouldn't put anything on the site I would be embarrassed if my mom saw, but that's up to you. Employers are checking these things out.
And I'd create a family site.... where you and your siblings can gather. Set up a once a week chat or something. I IM with my parents and we have a www.myfamily.com site... but that one costs money, there are others that are free.
I can't blame her for wanting to stay connected... she loves and misses you. But you need to take her off as a friend and not let her interact/comment.