It really makes me wonder how differently this might have gone down if, instead of you broaching the topic, your friend had taken your wife aside and said "I think I'm falling for you." Something to discuss, I suppose.
Of course the problem with the fact that your wife may have feelings for your friend is that if your friend has deep feelings for you but only sees your wife as a friend, your wife might feel doubly betrayed and jealous... but again, no way forward except through discussion...
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.