Complex sentence: Bledel dated her "Gilmore Girls" co-star Milo Ventimiglia from December 2002 to July 2006, and began a relationship with her "Mad Men" co-star Vincent Kartheiser in mid- 2012.
Split into simpler sentences: Bledel dated her "Gilmore Girls" co-star Milo Ventimiglia from December 2002 to July 2006. She and her "Mad Men" co-star Vincent Kartheiser have been in a relationship since mid- 2012.