"we're debating painting schemes on a home that doesn't exist yet"

It sounds like you're a willing participant to her face and hiding your feelings (which seem to be "ZOMG I'M SMOTHERING!").

Try ignoring the nesting activity and praise the good stuff. Don't participate in the safety-rating-checking, don't go buy a Volvo (unless you want one!), and eat as much red meat as you want. You're not powerless here. If she flips her lid, ignore it. She'll get the hint and either adapt or move on.

Honesty. Have an honest conversation with her and let her know where you stand. Open communication can only help a relationship. If she is truly the one for you, she'll respect your space and slow it down. If she has a hissy fit and freaks out, maybe it's time to re-evaluate the situation.