A.,
My two cents may be contrary to contemporary wisdom, but I say, let her be. Generally speaking, I think we can be way too high-strung these days about getting our kids to certain milestones by certains ages - they should all read in kindergarten, etc. All children are different.
Another reason I suggest just enjoying her and letting her develop at her own time is that I was quite a late talker, myself. My parents thought there might be something seriously wrong - and what did I do to shock them? Started speaking in full sentences. Note, I've never spent any time at the back of any class (okay, I can openly admit I utterly hated statitics) and, if you read through any of my replies on mamasource or most of my posts on my blog (http://www.tristansepinion.blogspot.com), you'll note that communicating at any length is not something with which I struggle. :-0
Finally, as I've started homeschooling, I'll offer up the observation that it can be easy to let something like this get under one's skin (especially if we know our child is bright, etc.) - but if we do, it's truly our problem, not the child's problem. My bet is, your daughter has her own timeline and, if you've checked with a doctor and know she's physically in good shape, I believe she'll develop as her own free will dictates, into a beautiful, happy, well-functioning human being. So - just enjoy your time with her now, while things are more quiet than not...!
Oh, and, just for kicks, go read a lovely book that had me struggling to a) not mis-prounounce the title in a room full of small children at the local public library and b) fighting back the tears such that my own child kept asking, "are you crying mom?" and I kept having to reply, "it's....it's...SUCH A GREAT BOOK, isn't it?!!!" - go read "Thank You Mr. Falker."
I wish you great joy.
Warm Regards,
T. Benz