20 pounds is hardly "keg" on some frames... for many women that could near entirely be in their chest without appreciable gain elsewhere (rare, but it happens).
This is an oversimplification, but:
click. Height REALLY matters, and distribution/body type does as well. Different people wear the same amount of weight differently.
That being said, who cares what someone else finds attractive? The relationship could be based purely on mental and emotional stimulation, or it could be a marriage/coupling of convenience. Doesn't affect you, and doesn't really matter.
Personally: It depends on the person.