you and Hange arrived at marely and while the others went off exploring and trying new food, you and hange took a walk looking at the waves

You were really chatting her up earlier so you've got her in a good mood. You knelt on one knee to tie your shoes while she was looking at the shore before turning back at you

“Oh my GOD, he’s PROPOSING. This is real. This is happening. He’s proposing. I didn’t even brush my teeth properly this morning! Levi’s gonna kill him. What if he has a ring? Oh no. What if he doesn't? Wait—what if this is some weird prank? No. He’s too sweet for that. Is this why he was nervous earlier? Oh gods, I can’t breathe—why is this romantic? I’ve dissected Titans with my bare hands and this is what breaks me?”

She's already flipping out, your basically left with no choice but to go along with it. The universe already set you up, so you cant fumble.