The middle-aged Pennsylvania couple had lived together for more than a decade, buying a home together and sharing other assets. They never got married. It didn’t matter, they thought. But after he died of cancer recently, leaving her his entire estate, it did matter. A lot. Pennsylvania is one of a handful of states that still imposes an inheritance tax–a tax on transfers from a person who has died to the people who inherit, with rates based on the category of recipient. Transfers to spouses, but not to unmarried partners, are exempt. Pennsylvania subjected everything she was left to inheritance…