No, Mary did not sin.
(all Christians believed this up until a few hundred years ago)
The Bible does not say that Jesus is the only one without sin.
I know some people have made different Bibles than the rest of Christianity, but even those do not say that.
Give us a few more hundred years and you will have groups who believe that Jesus sinned and had kids. As time goes by the truth becomes more and more muddled the farther people get from Catholicism.
Look at Jesus as God and you will see that Mary did not sin. But neither have babies, retarded people and angels. Just because we sin doesn’t mean that others have to. Sin is not required it is something we choose to do and pretty much all of us do it except for those few exceptions.
(well, now that we are killing hundreds of babies these days the exceptions are much more numerous)
In Christ
Scylla