Inspired by the lines: "I would take a bullet for you just to prove my love, only to find out you are the one holding the gun.
The situation was awful. You were a spy for an agency that was the competitor to the BAU. Fate works in weird ways, you were sure of that once you met Spencer Reid at a casino, both of you out undercover on a mission to catch the UnSub. One thing led to another and now he was at your door with flowers and a plastic bag full of everything you've ever mentioned wanting (he had an eidetic memory, so there was literally everything.)
"No, I swear, I'd do anything for you, I'm in love with you, I've never felt this way about anyone. I would take a bullet for you just to prove my love-." Spencer explained over and over again, making your heart swell each time. "No, Spencer, I won't date someone with a job like yours, forget it." You sighed, slamming the door in his face. He had told you about his career and suddenly everything hit all at once, your job, the BAU, your competitor, your enemy, your boyfriend. So you made up an excuse not to see him anymore.
He kept insisting, you kept denying. It was a cycle by now, by the time Spencer did actually take a bullet for you...
On a mission from your agency, you were about to get shot by the UnSub and your group of agents did not have your back, in fact it was their idea to risk your life for the win against catching one of the most dangerous UnSubs, preforming much better than the BAU team. Even with your life at risk, there was no doubt they'd get the promotion. So, one thing led to another and Spencer, the hero, took a bullet for you.
At the hospital, you had to explain everything to Spencer, what you were doing at the crime scene, about your team, the competition, your lies about your career and the reason why you wouldn't date him. He was angry, tired, but angry.