I'm not sure she's correct about milk melting faster than cream or that the "deflates" if you whip too much air into it.
One of the three main differences between the ice cream and gelato is air content. ice cream has more air and doesn't loose it over night; it would be bubbly too with all the air escaping. Gelato melts quicker because it is served 10 to 15 degrees F warmer than ice cream (this main differences).
Low air content and warmer temp is why gelato is smoother.
Source: My Italian wife and I have had long discussions and Internet searches on the finer points of this topic. I'm not an expert, I could be wrong.
Gelateria Dondoli in San Gimignano is amazing. They are very proud of being a gelato "world champion", which honestly made me a bit skeptical, but it was delicious.
Milk with a higher cream content than even full fat American whole milk. There was a gelato place near me that had an Italian trained master he imported his milk. I was very sad when he retired.