Jason, if you didn't watch last season, then you aren't going to know who she is.
Tony met Gloria Trillo at his shrink's office, she works at a Mercedes dealership and he had an affair with her. She went psycho when he wasn't around for her, or if he didn't show up for dinner when expected, etc. Your typical jealous psycho-chick.
One of Tony's crew (Pat Parisi?) finally had to tell her to back off. He said something to the effect of--if she didn't his face would be the last one she saw, not Tony's.
She then disappeared for a while.....only to return next week!