Looks to me like in the second image she’s covering her breasts with her right arm (which is bent at the elbow accordingly) and holding a blaster in her left hand. Though I guess it could also be the top of her dress, with her right arm held behind Luke’s back.

But the first sketch does look like Leia is topless: her skin tone is drawn slightly darker than the loincloth she’s wearing. And in the third image her left breast has popped out of her shirt while she’s being tortured (you can see the line where the fabric has slipped under her bust).

Also: this sort of thing is probably the real reason why Lucas thought Leia wouldn’t wear a bra under that dress.