She has definitely sex'd herself, and is starting to form calyx around the pistils. I wouldn't call it "pre-flower" yet until the growth points start showing more pistils than new leaf, but that is really up for debate/my personal choice. I'd say if you've flipped to 12/12 for a week and this happened, by next week you should enter pre-flower/flower.
If an auto, then give it a week and it'll be flowering.