How Can I Possibly Get An A In This Class If........?

The teacher (Honors class) grades things without a rubric, she will never give anything an A unless its perfect, and if it's perfect, she won't give it 100%. She takes points off all the time, and she doesn't give anything back, or tell us why we got points off for something. It drives me crazy when i do everything she asks for flawlessly, and i don't get full credit. An example of this would be this picture i spent 8 Hours of portrait for a book review, and i followed the guidelines exactly, and i am not the best artist, but she only have it a 90, because she has seen better in the past. Another example would be this photoshopped picture i spent a few hours on, and it looked really good, and contained all of the aspects she asked for, when she got it, she said she loved it, and that it was one of the best that she has ever received from this assignment. she ended up giving it a 90. which is better than everyone else i guess, who got 70s, and 60s. it drives me crazy that whatever i do for her, I never get credit for what i do. I have a 89% in that class (which is good considering 3/4 of the class is failing), which stinks for me because i really want an A, and I have an average to maintain. what should i do? whenever i ask her she doesn't want to talk about it, and i find it hard to learn from my mistakes if i don't know what i did wrong.