I'm a speech pathologist in training - in my 2nd year of graduate school. A typical 2 yr old should have about 50 words in her expressive vocabulary (what she speaks). The receptive (what is understood) is typically much higher, even in non-typical children. I would get her evaluated. It won't hurt a bit. And by doing it so early, you will probably be saving yourselves a lot of money if she does need therapy. It could be all sorts of problems like apraxia, an articulation or phonological disorder (a speech sound errors) or just a simple delay in language.
What is important to remember and I'm getting the jist that some of the parents in this thread didn't, is that you do not have to be cognitively impaired, "dumb", "slow", "not normal", or any of that negatively associated feelings that come with attending speech therapy. Don't let your pride of having to admit that your child needs a little extra help in something get in the way of actually getting the help. And don't let your pediatrician dictate whether you get speech treatment or not. Most of the time, they are off in what they are telling you. My 3 yr old nephew was told that he'll grow into, he's a boy, etc. Well he is currently in speech therapy for a severe phonological disorder. In just a few months of therapy, he was a whole new person, but he has a ways to go still.
Just curious, but has she had a lot of ear infections or a hearing screening recently? Do you notice anything at all, even the littlest things in her behavior or movements aside from the speech? Not that I could still help you, but if you do have her evaluated (which I think you should), she should have a hearing screening, a language evaluation, a speech evaluation, an oral-motor exam, and maybe some smaller informal tests. This is typical for an evaluation and is done in our clinic on every single person that comes in the door for treatment. You should also receive a gigantic form to fill out for a case history that will help the SLP before she does the eval. Keep us posted on what you decide to do and if you have any questions, I'd love to share my knowledge.
*Shannon