W.W.
I would go straight to the doctors. What other things is she doing? Is she doing repetitive things, is she acting like she is deaf and ignoring you when you call her name, has she been distant, is she lining things up, is she having gut issues? Maybe go to a person who is experienced with developemental delays. It may be nothing. She may have an ear infection and can't hear well right now. Don't panic but definately see someone.
I wish you the best. My son did that at 17 months and has autism, but it does not always mean anything. Lots of the things that special kids do normal kids do too.
W.