I want to offer a slightly different take on what GCC and Prog have talked about.
I do think it is important that your partner is ok with fire ing and I do think that convincing a soon-to-be-spouse is possible and essential. I say this because if I were the one dragging my heels on fire ing I would resent my spouse not working as I sit in my cubicle. The thought process wouldn't be "Oh look, things are still going well even without her working!" it would be "Well of course things are going well. I am working and making sure the ship is still steering straight ahead. Look at this one particular month that our investments took a hit!".
Instead I urge you to work on showing how your investments are meeting your needs. Discuss what the long term vision is and why an extra $250k is needed.
The way that I see it is that FIRE is a big, lofty goal and it is great to be able to say that I would FIRE immediately after my goal but something quite different to be faced with that decision. The fear of failure is a perfectly valid fear and I want to ensure that my wife and I both go into the next stage of our life confident that things will be alright so that we can enjoy our time together. If my wife comes to me asking to work for another year, I will push back and try to read what the underlying issue is but will ultimately work to make sure that we are both comfortable with our strategy. Anxiety and stress is not something I want to go into FIRE being burdened by. I will leave that in my cube where it belongs.