There could be a fanfiction where Sakura is jealous because Naruto is spending a lot of time training with Sasuke again. In this story, she feels left out and her jealousy might lead her to train even harder herself to prove that she's just as important. She might also try to come up with reasons for Naruto to train with her instead, like saying she has new jutsu she wants to show him.
In some fanfiction, Sakura could be jealous when she sees Naruto getting praised by other villagers more than her. This jealousy could fuel her determination to do more medical and combat missions. She may also try to show off her skills in front of Naruto more, in an attempt to gain the same level of admiration from him.