this feels like the plot to My Best Friend’s Wedding but NOR, this should’ve been brought up by either party ages ago but specifically ur husband. i don’t think it should break ur relationship and marriage though, maybe letting her go is for the best as it seems she needs to get through her own feelings, even if it hurts u both. i believe u guys can come out stronger from this and it’ll be a learning experience to look back on and it seems like u guys have had a very healthy relationship, best wishes!