If your baby is totally reliant on milk for his/her nutrition then formula is best but once you start feeding solid meals and they are getting more nutrients that way, you can switch to cows milk.
Sounds like your LO is on a great diet - I would go ahead and change her over, she's getting a great range of other foods - just need to make sure she is getting plenty of protein too (meat, fish, egg yolk)...
Trisha.
