S.M.
Hello J.,
My son is six months old, and we just started to give hima aippy cup, and i have found that the avent sippy cups work great for him, he is able to get the liquid out with no problems, the playtex ones seem to be a bit harder for him right now. And with the whole warm milk thing, i would warm it up and put it in the sippy and then little by little let it get colder, she will get use to it, it won't take that long.