She resurfaces at Cathy 's birthday party after a long absence .
Cynthia Nixon as Rebecca ( Seasons 1 and 2 ) , Cathy 's college roommate and long - time friend .
Cathy resurfaces at Cathy 's birthday party after a long absence .
Cynthia Nixon as Rebecca ( Seasons 1 and 2 ) , Cathy 's college roommate and long - time friend .