What is your opinion on this description?

Not bad, not bad. But you switch tenses a little bit. You say "wore"(past tense) then you say "stops"(present tense). I think the second sentence needs a bit of reworking to make the most sense. Perhaps say "The dress' colors against her shining black hair, which stopped at the end of her hips, had just enough contrast to work perfectly." I changed onyx because when I think onyx, I think a shiny black gem, not really a hair color. And I would rewrite the last sentence, too. Maybe "She completed the outfit with a handmade crown of black and white roses". Just remember that less can sometimes be more :)