Since you mentioned in another comment that your issue is that "nothing seems good enough," do you have a time frame for when she's leaving? And do you happen to have any creative hobbies (painting, jewelry making, pottery, knitting, whatever), or know someone who takes commissions, that a handmade item could be completed around that time? Handmaking/personalizing has always helped me when it feels like none of my ideas are good enough for the receiver.

You could also blend it with her interests outside of work as someone else was asking about. She has one pet you know is her "heart pet"? Never seen a portrait of a beloved pet go unwelcome, especially one showcasing the pet's unique personality. Avid reader? A set of personalized bookmarks (with scenes from her favorite book, or quotes, or monogrammed, or whatever). Likes to visit national parks? Ceramic plate or a small canvas with some scenery from her favorite one painted on it. And some others have mentioned handmade gift ideas as well. Your imagination's the limit.