You're mom thinks you're a star! Of course she wanted you to get in everywhere. If you already have numerous acceptances, there's really not much to tell her other than "Mom, I have plenty of other choices. Very few people get into every school they apply to." If your mom is like mine, any discussion of grad school makes her weepy, so I just settle for a "Ma. You knew this was coming. It'll be fine."
And then my mom cries about how as soon as she knows I'm happy she'll be free to die, but ya know, some moms are more dramatic than others.