If you have a reference picture, it's better to always post your picture alongside it if your goal is to reproduce it.
Anyway, that picture is beautiful. It is a REALLY challenging one, though, requiring advanced sense of what the light/shade is doing, facial perspective, hair physics, etc...so if you can't wrap your mind around it, don't feel bad.
Currently there's a bunch of fundamental things going wrong in your picture that would cause you to end up with a completely new face if you kept going. To cover a major one, her face isn't drawn in the right perspective. The picture has her face slightly at an overhead view while yours is in a level view. A couple ways to correct this is to make her forehead taller and make the contour of her left side of her face more vertical. Also, her mouth need to be bigger. Make sure you pay attention to her lower lip; more of it is seen in this perspective. The nose is also wider at the base.
For images like these at your skill level, I strongly suggest using the grid approach.