Treat them the way you’d like to be treated.
It’s over. If you truly have to fire (vs. demote in some fashion) your co-founder, the relationship is broken. If not forever, at least probably for quite some time.
So first, my advice is slow down. Are you sure there isn’t a role she can succeed in? If so, try one last time. And get some outside help to work you through this discussion.
But if there’s no chance it can work, be nice about it. Be direct. Be grateful. Just imagine if the shoe was on the other foot.
A bitter, angry ex-founder can drag at least a small cloud over the company for months and even years. Lawsuits, drama, whispers, bad Glassdoors, and more. The firing is often just the start of a dragged-out process.
Try to make it as quick but also gentle and appreciative as possible. Probably, she helped you get where you are today. Even if the help tapered off, and wasn’t as much as you’d hoped, or needed.
