well in the preview picture, she has about the length of her head of cleavage sticking out, thing is, it looks pushed up. if it isn't you're looking at about 8 inches of bust, putting her at a 42" bust or H-cups
The shot is sort of looking up at her from slightly below, like a worms-eye view maybe. But if her bust is being pushed up is probably open to interpretation. Her breasts are about 3/4ths the size of her head (and because it's not a common size for me there is probably more variation than normal). But I wanted to make her small enough that I could move her up to head-sized without going into another range if I ever wanted her to grow a little more. And also she has kind of a unique size compared to other characters I've drawn which is kind of nice.
An opinion (so detailed that I felt like I had to include) from DA was:
She looks very similar to a slimmer leanne crowe (44-30-38 = 34k, 5'7). Definitely perkier and fuller than Anya sakova (40-25-36 =32G, 5'5) but also has more hips and a bigger butt than Anya. I'm guessing she's got a 30" band, and I am guessing Aonar is right because a smaller band and same cup as Anya would look proportionally bigger.
So, running numbers from those, I'd throw out:
30g,-26-37 = 38-26-37
Most extreme (if she's thinner than I estimated above) I'd say 28h-25-36 = 37-25-36.
Not claiming any expertise, just guessing.
Although I like your estimate better
The average guess was "G", with one "H", and one "F" I think. I thought the result would be higher, but I probably didn't consider before that I'm comparing her to models who are much taller. I'm kind of happy/satisfied with the hips estimate, I've tried to make her more shapely over the years (she started out almost straight up and down physically). A 5' 3" asian with 37 inch hips would probably be pretty impressive.
Maybe I should split the difference between 42" and 38"?