As a fictional character of mine once remarked, "Welcome to my world. Enjoy your stay." I wish I had advice to give you, but the only thing I can really offer is that you aren't the only one.
Read the article that superfantastic posted a link to and try to get your mom to do the same. A lot of parents have a difficult time accepting that their kid could be something other than "normal". Most parents don't like to see their kids struggle with stuff and for some reason or another (don't ask me why this is), they see anything that may be either wrong or different about their kids to be a reflection on them as parents.
In time, she'll probably come to accept the fact that you have AS, but do remember that this news is rather shocking at first and can take awhile to mull over and even begin to accept. In the meantime, you'll just have to accept the fact that she's having a difficult time dealing with it.
Also, it probably isn't a bad idea trying to find another trusted adult to talk to about this. It could be a teacher from school, a family friend, a neighbour or a counselor or anyone who is willing to listen and help make suggestions if you're having problems with something specific.
Hope this helps.
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Itaque incipet.
All that glitters is not gold but at least it contains free electrons.