The same question and answer is brought in Moshav Zekeinim
http://hebrewbooks.org/pdfpager.aspx?req=20791&st=&pgnum=106
Regarding halacha l’maaseh, R’ Moshe Shternbuch writes that he has seen Dinah brought as a raya the other way – that despite being conceived by Rachel, she is called “Bas Leah”. He then says that you can’t bring a raya from ma’aseh nissim. http://hebrewbooks.org/pdfpager.aspx?req=20026&st=&pgnum=545