For some reason, actually showing a nipple/aureola is the exact point, as far as modern Western culture is concerned, at which a teasing display of cleavage becomes actual nudity.
Some artists seem to deal with this by surgically removing the problematic nipples, a la Barbie. This allows them to freely draw technically-naked women hanging out any which way they like - no nipples, no nudity! But what has always given me the utter body-horror heebies is when, instead, they apparently transplant the entire nipple to a random part of the breast that happens to be covered.
Obviously every pair of real breasts is different, and every real woman’s nipple size and placement will vary, but generally large breasts have medium to largish aureolas placed at or slightly above the “peak” of the breast. Going from that rubric, and using my own body for reference when I was unsure, I threw together a quick illustration of the mysterious migratory nipple phenomenon: