Women who breastfeed have more sensitive nipples. Does she still have any drops of milk that leak? Many women, even years after finishing with the baby, still get milk drops as they climax in intercourse.
Yes, the wonders of pregnancy....first the tits are swelled and the skin distended by the production of milk, then if she breastfeeds ( 6 months? A year?) The milk is continuously pjmping into the tits and then being sucked out and deflating them. In the end the skin just gives up, becomes loose and when the woman stops breastfeeding her tits flop and reduce snd become nice little hanging bags empty and flopping. Is your gf like thst? Are her nipples very sensitive?