There is ample evidence linking hormonal contraceptives and also abortion to breast cancer for those who study the issue closely. Start with the fact that the incidence of breast cancer has increased by 40% since 1975. What would cause this? This is what started the good doctor down the path to scientific truth.
In the following textbook, Bland KI, Copeland EM. The Breast: Comprehensive management of malignant diseases, 3rd ed, 2004. Epidemiology of Breast Cancer, the text states that the increased risk from induced abortion after 12 weeks of pregnancy is 38%. There are a vast number of studies as well, the majority of which link breast cancer and abortion. Specifically, this is an abortion prior to the first full term pregnancy.
Estrogen in hormonal birth control has been considered a carcinogen by the WHO since studying the issue in 2002, and the NIH lists estrogen as a carcinogen. The estrogen stimulates breast tissue growth, which increases the number of potentially cancerous cells. The increased risk here is also approximately 30% or greater.
http://www.cancer.org/docroot/PED/content/PED_1_3x_Known_and_Probable_Carcinogens.asp
http://monographs.iarc.fr/ENG/Classification/crthgr01.php
The American Association of Pro-life Obstetricians and Gynecologists (AAPLOG) has a couple good articles debunking those that say there is no link between abortion and breast cancer: http://www.aaplog.org/downloads/AbortionComplications/Induced%20Abortion%20and%20Subsequent%20Breast%20Cancer%20Risk.pdf
Dr Lanfranchi is not alone - the data is on her side, and I commend her for speaking the truth.