In the UK, from 6 months the minimum requirement is 20 ounces which is inclusive of milk on cereal, in foods, dairy products such as yoghurt, cheese, etc. They dont have to take the whole lot as a drink as you can substitute other foods containing calcium, etc
If your lo is happy with the amount she is drinking and you are giving other sources of calcium I wouldnt worry at all. These minimum requirements are based on the 'average' baby and not everyone has one of them!!
Seona