I'm an early bird with a reluctant (read: grouchy) morning partner.

: He's horrible in the morning, even if there's WDW fun in his future! Hence, no morning ADRs for us. I couldn't imagine inflicting his grumpy-ness on strangers! (that's why he's gonna be Grumpy for
MNSSHP this year) LOL
I think it's all in the delivery. Assuming you're with kids: Tell her, "Honey, I decided since this was YOUR vacation too, I'm going to let you sleep in and you can meet us at [insert attraction / location here] at [insert time here]. Or you can call me on my cell when you're ready for us to meet you!"
That way she thinks you're doing her a favor by getting out of her hair and letting her have a glorious child-free morning all to herself. You, on the other hand, get to go to TH and enjoy breakfast with the characters! It's a win-win situation!
If you're like me and it's just the 2 of you, you can go the "good guy" route by honoring her wishes and missing out on breakfast, or go the "bad guy" route by nagging her until she complies! LOL

Hey...I didn't say it was gonna be PRETTY!
Either way, you're all at WDW, so you're going to have a fabulous time. Enjoy your vacation!