Both my boys went onto cows milk when they were weaned at 13 and 14 months respectively. DS2 wasn't keen to give up the boob so I tried formula thinking it might have been the cow's milk he didn't like, but he refused the formula completely. Can't blame him... it tastes horrible!

My understanding was that they can't digest cow's milk protein very well early on so you introduce it later. If your DD hasn't shown any igns of intoleranceor general digestive issues then I wouldn't think it was a problem.