Given that a lot of Leila's close-ups were shot soft-focus, the hair could have come from her good-bye scene in the transporter room at the end of the episode (the angles seem to match) while her face had to be found in another image.
I just don't buy that. It would be hard to get the angles to match perfectly. It's far more likely that the artist simply found a screencap that isn't on TrekCore. As I said, that image does look familiar, as though I've seen it before. It could be an on-set photograph used for publicity rather than a screencap, explaining the sharper focus.