Both of my children had limited vocabularies until their second birthdays. Then it seemed like overnight they added several new words, spoke in short sentences, and started verbally communicating their needs. I had spoken to the pediatrician when my oldest was around 18 months. She said to watch for other language skills - the addition of ANY word, body movements, facial expressions, intonation in their babbling, following simple directions, responding to his name, etc. As long as I could see him using those forms of communication then there was likely nothing to worry about. She was right. She explained that some kids put so much energy into playing, moving and exploring that they don't talk as early.
Both of my children's first words were variations of 'mama' and 'dada'. 'Ball', 'yea', 'wow' were early words followed by 'woof-woof' (for dog), 'ashes' and 'down'(from Ring Around the Rosie), 'again' and 'tickle'. We used to tickle them and say "tickle, tickle, tickle, tickle, tickle". They picked up on that and repeated it as 'ducka, ducka, ducka, ducka, ducka'.
Try not to worry. My bet is that you'll see a big change after her second birthday.