Look at pics from pre-WWII and then look outside. She's right, you're probably fat. It's our perspectives that have changed.
Pre-WWII we were coming out of the great depression. Go back to the 1890s-1920s and you will find some heifers.
During the Renaissance and Baroque periods, many of the nudes were rather chubby.
You're right. But...obesity wasn't anywhere near as prevalent then as it is now.
That is for sure.
Excepting maybe during the heyday of the Roman Empire. But who wants to go back 2000 years.