My daughter always had warm bottles, and when I introduced milk, I just did it cold...just the way we all drink it at home. I think you could try it this way and if she absolutely hates it you could warm it. You can just experiment both ways and soon enough you'll figure out what works for her
I also like the idea of mixing the formula & cow's milk together during the introduction period. I remember when I switched my daughter over she got sooooooo constipated we had to use suppositories on her
The mixing is definitely something I will keep in mind when the time comes to switch my son over.