Landlord died, who owns the house?

In Pennsylvania, my landlord died and his live-in girlfriend claims she’s now the landlord. I guess she’s going on the whole “common-law wife” bit, but when he was alive I wasn’t even allowed to give her the rent! he knew she’d spend it. Her name was and is not on anything having to do with the house, deed, bank accounts, etc. When landlord died, he was in the process of fixing some things. They still haven’t been fixed so I stopped paying rent. Legally, I wonder who owns the house? He has no family that has come to claim his property and if “possession is truly 9/10 of the law” then don’t I have a claim on the house? Also, if she sells it (to me) and her name isn’t on the deed, if a “legal” claimant comes along, can they take the house away from me? I have an appointment with a real estate attorney next week but in the mean time was curious if anyone out there had a real clue to what my rights could be. Thanks.
Thanks, you guys are giving me some really good idea and thoughts. I have no intention on just not paying rent and going on a shopping spree, but I just don’t want to pay her the money, because as I said, I don’t trust her. She claims she’s the executor of the estate, but I haven’t seen anything in writting to this affect. I think I’ll take a trip down to the Register of Wills and look this up. Until then, I’m putting the rent in escrow. Thanks everyone.