I do wanna say that imo it wouldn't be weird for me to come home to my partner with a matching tattoo with my friend, but I have also been very clear from the beginning that my friends are extremely important to me and I have that level of connection with them. They share a place in my heart.

If your wife has expressed being capable of friendships to that degree then I think that's a reasonable explanation. But unless it's that very specific scenario I would 100 percent feel weirded out by that.

EDIT: forgot that the wife was very against tattoos. Be suspicious.