In these cases of a couple, it is best to omit, you do not tell the truth, nor do you lie, since as you say, nobody learns from the experiences of others and each one has to acquire their own teachings, the sad thing is that although that may not end , you may have to endure years repeating that woman the same scene,
Something similar happened with my sister's husband, until one day she invited me to accompany her to her mother-in-law's as she wanted to verify if her husband was really at a job interview and the man was at his mother's house with a friend, that day my sister's blood pressure rose to 220, I had to take her to a hospital,
while her husband got lost with his supposed friend, to summarize the story for you, after that I was left in a bad light for wanting to defend my sister and she has been holding horns for 22 years, that's why I learned to see the bulls from afar. Hopefully your uncle if he opens his eyes. Blessings 🙏🏽🤗