My daughter has autism but she is social to some people?

My daughter is 2yrs old and was diagnosed with autism(moderate to severe). But this is so confusing to me because she can be very social and over the top with affection. This is only with people she knows. On the other hand she has no language, she bites, scratches and pinches herself and others. she have extreme sensory issues. Put it like this, she has all the signs of a autistic child but i can't understand her sociable traits. This is really hard for me to understand.