Preceptor Problem

Hello everyone. This is my first time posting on this forum. I am a newly graduated PN student and I have a problem that I would like to get some feedback on. I just completed my preceptor program last week and I graduate this friday. My problem is the fact that my preceptor did not go over my evaluation sheet with me. I thought I did fine. We worked in the rehab unit of a local hospital for 3 weeks and in that time she never corrected me, reprimanded me or anything of that nature. She did make some suggestions that I document the patient';s ability to ambulate and take care of toileting needs, which I did after she told me. I was always prompt in arriving 30 minutes before our shift, clean, hair back, no makeup, completed my med passes accurately and on time, no problems as far as she ever let me know. When I picked up my evaluation sheet from her to take to my school she had it in a sealed envelope. I got a call the next day to go in and meet with the director of nursing and she had given me all 3 or 2's on a scale of 1 to 5 and said that I needed to work on my communication, self reliance, documentation and even rated me a 3 with is average on promptness and behavior. I was shocked! Virtually all of my feloow students had 4or 5 on their evaluation points. Besides that she had forged my signature on two places on the form I was supposed to sign, never showed me or told mewhy she was rating me this low. My instructor asked why I signed it and I told her I hadn't because I had never even seen it! She agreed with me that it was indeed not my signature.
I am really feeling like I am a failure, but I had felt that I had been doing a good job and received no input otherwise from this woman in the three weeks I worked with her. I even listened to her story about her hysterectomy everyday, like I had never heard her tell it before. I am wondering if she did this because she disliked me personality wise. I am fairly quiet, but she asked how old I thought she was and I said I thought she was in her 50's and she seemed taken back and said "well, I am only a few years older than you." Another thing that was said was the day that I was leaving an RN told me "You know J... never gives good reviews to students." I laughed it off at the time , thinking she was just joking, but now I have to wonder. She has mentored several students in the past, but I do not know any of them to ask them if they had similar experiances.
I am graduating on Friday, but I have really lost confidence in myself and I feel like my instructors are now looking at me like I am a bad nurse. I really want to confront this woman in a nice way and ask her why she rated me the way she did, and exactly what she feels like I did wrong, since she didn't even have the decentcy to talk to me before she turned in my evaluation and signed my name on the papers herself. On the other hand, I don't want to rock the boat, since she works at a local hospital that I will likely work at in the future.
I would just like some input on what other students, nurses and even other preceptors feel about this. If she only would have let me know I wasn't working up to her standards, I would have strived to improve my performance, but she never said a word in correction about anything, even said "good job" to me on several occasions.