- op 6/ 1 has a section with an ONGOING light trill while the melody is still being played. Not an easy skill . Try just play the RH of these measures.
First, since you have a teacher, why don’t you let your teacher assign you pieces that will help you prepare to play this grade 9 Nocturne? i.e., easier preludes and nocturnes would be a good start - your arpeggios will need to be fluid and sound effortless - you will need to effortlessness voice a chord (I.e., play multiple notes/voices in one hand while making the melody prominent in the same hand - op 6/ 1 has a section with an ONGOING light trill while the melody is still being played. Not an easy skill . Try just play the RH of these measures. If you learn it now, it will sound like a student that learned it too soon and struggles rather than an accomplished pianist who was able to negotiate the beauty of the music.
Certain pieces are difficult to play technically, but easier to bring out musically. Some are the opposite. I think this nocturne is of the second kind. There are so many meandering melodies, and multiple voices going on which I can hear, and so it doesn't seem straightforward to comprehend and bring out musically. Playing a mediocre version of such a piece won't really make any sense. Although you say you are a good memorizer, you have only worked on easier pieces before and this looks like it will be a real pain to memorize, especially if you have no prior experience with Chopin AND can't read well, as you stated here. Why don't you learn a few other Chopin pieces (other waltzes, nocturnes) before you come back to this? If you're truly ready for it, it shouldn't take long.On the other hand, I would suggest just attempting to read through the piece if you can. That way, you'll see for yourself where the difficulties of the piece lie. You should also ask your teacher why she thinks you're not ready, as that can give you a much better idea.
Of the two, op 62 no 2 is the easiest technically, but they are both difficult. Not in the sense of being flashy technically, because they are not, but in terms of the technical skill needed to pull them off. You need a certain degree of relaxation combined with fine control over the fingers to play any Chopin well, imho.