Graffiti #7 is in the hospital to your right side at the beginning of this scene. On the starting point turn right and go in the direction of the double doors and you will trigger a cutscene with the couple from Episode 2. After this cutscene interact with a nurse poster on the cork board.
For a visual guide open the spoiler, inside you find my video with all 10 graffiti locations.
*** Spoiler - click to reveal ***00:08 - Optional Graffiti #1 (American Graffiti)
00:43 - Optional Graffiti #2 (Extra Credit)
01:16 - Optional Graffiti #3 (Peer Review)
02:05 - Optional Graffiti #4 (Monthly Masterpiece)
02:53 - Optional Graffiti #5 (Spit Take)
04:38 - Optional Graffiti #7 (Hello Nurse)
05:26 - Optional Graffiti #6 (Venting Machine)
06:53 - Optional Graffiti #8 (A Penned Appendage)
07:57 - Optional Graffiti #9 (Drunk Drawer)
08:41 - Optional Graffiti #10 (Messed Up)