If you read the post manga pages, it means her skin is very smooth which is kind of weird because we describe things as having a "Peach fuzz" but I guess it's different in Japan.
Thanks for taking a look at the info pages!
When talking about asian beauty, for sure "flawless" can mean "very smooth". No big pores, wrinkles, blemishes, etc. So the smooth skin of a peach can be comparable. There's also a preference for natural and youthful beauty. Vellus hair known as peach fuzz/baby hair is something we all have since we were born. There's definitely a cute juxtaposition in this chapter between the prickly and thickened facial hair of a man from growth and shaving and a girl who still has a baby smooth face and only peach fuzz.
So momo-hada describes beautifully smooth skin that is natural (little hairs and all). The closest English equilvalent miiight be "peaches-and-cream" but it's usually used to describe a situation that goes smoothly. But when the idiom was popularized in the 19th century as it was a popular desert, it described a woman with beautiful and fair skin.
Take a look at a few Japanese beauty products. Look for 桃 肌 (momo hada).