the eyes have to have that friendly, surpised look. Most likely , the nipples will be harder, but not usually rock hard like when you are cold or scared, just more firm. Coloring is important too. You need to add a warm flush, about 3 shades redder than your skin tone, between the breast, on the lower stomach, on her genitals, and often on her cheeks as well. If she is clothed, these arent necessary, though from what I seen, women who are aroused in clothing usually get really uncomfortable wearing it, so also make it look like she is a little uncomfortable without being i hate this uncomfortable.