How did you come out the first time? Is it possible she misunderstood or thinks you're bi?
I asked if I could make an appointment with the therapist I used to see (middle school.... was a bad time for me, filled with violence, suicide attempts, and tween angst), which kinda surprised her cause I had been fine the past few years. After going to that appointment, I sat down with her and told her. She said she wasn't surprised (we have a bunch of gay people on both sides of the family), and that she loved me and would support whatever I decided.
I had all of 1 girlfriend in High school (the token "your a senior, time to date a freshmen" relationship) that lasted all of 5 weeks, and we never talked about my (non-existant) romance life while I was away at college.