One thing to keep in mind is that the bed bug registry is only as good as people who are reporting. It could be that the people who reported in 2010 moved out and no one has thought to report since. The property manager is not bound my law here (like they are in NYC) to report bedbug history to prospective tenants and managers know that bedbug rumors fly fast and can totally kill a building’s rentability. So, take what she said with a huge grain of salt… talk to some of the other residents (in the same floor as the unit you’re looking at). This is a huge risk you’re taking – if you move in and do have bedbugs it’s not just a matter of moving out. You can take them with you.
Personally I wouldn’t take the risk.