Some considerations:-
how old is she? Older = less risk, younger = more risk
what's her reputation? are you going to sink yours by being seen together (you will be, so assume you will be)
what's her track-record? butterfly? user? manipulator? or better hidden than a secret agent's real history?
do you have anything on her that can assure her silence?
and everything the bros have said above
Generally speaking you're MUCH safer playing away from 'home'. Pros, or if you have to have a girlfriend, find one away from work. BUT there are reports of successful office affairs ... so it's ultimately up to you to assess the potential downside ... the blow-ups are big when they happen.