Could my daughter be autistic?

[mball172]

My 21 month old failed the MCHAT at 18 months.  She did not point to things at all, rarely imitated our faces, eye contact was constant but for only a few seconds at a time, and occasionally didn't respond to her name.  She also did not speak at that point.  She used to babble but it only occurred every now and then.  However, soon after the test was administered, she started pointing to everything for help and interests.  She started imitating our mouths and started talking.  She only has a few words but her receptive language was tested at a 2 year old level.  Her pediatrician, speech therapist (and another one that evaluated her), and early interventionist do not think that she has autism.  However, with the failed MCHAT, it still scares the heck out of me.  She is very social although she has to warm up to the situation.  Meaning, a child can't come up and hug her to begin with but can after a short while.  She chases other children around at the park and plays alongside of them.  She has begun imagine play although it's just for a short while but loves feeding her babies.  She brings things to me and draws my attention all of the time.  I guess my main question, is that are some children that far behind and still develop normally?  She doesn't seem to have any of the classic symptoms.  She does spin in a circle occasionally because I taught her during a song.  It takes one or two times and she's dizzy, laughs, and falls.  No lining up of toys or any abnormal behavior.  It just seems that she is so behind peers her age, yet doing well at the same time.  To me, she seems "off."  Am I just being paranoid over the failed MCHAT?