Not really. How do you know that these women would readily admit to having abortions?
Obviously, you cannot help what one woman doesn't tell about her past. However, I don't see why a single study couldn't find women with abortions in their past, and their incidence of breast cancer as a population (all these questions are covered in any medical history). This incidence could easily be compared against women without abortion in heir past and thier incidence of breast cancer. It either is or isn't statistically significant.
Just because abortion may not lead to an increased risk of breast cancer doesn't make it ok. If you can't draw a link - let it go - it's just scare tactics and propaganda after that. If you want people to take you serious, then give them the facts and just the facts.