I can't get the option for the "reporting for duty" dialogue. I tried attacking her, freezing her, luring a dragon towards the camp. Nothing works. I've already done a few quests for the Empire. I've defended Whiterun, I captured a Stormcloak Courier, and taken over the firs fort (Fort Dunstad or something like that).

I've already beaten the Main quest line, including the peace treaty on top of High Hrothgar. Does shifting the Jarl's do anything to mess up the civil war quest?

I had the exact same issue, and I tried the same things. Bringing the dragon to the camp solved it for me, but only if she engaged it.

I lured a dragon from a word wall and it didn't work, and today I was lucky enough to have one spawn after I fast traveled to the camp. Still no luck. This is pretty upsetting. The 2 missions I've completed already were very fun and was looking forward to some larger battles.