Pardon my saying, but they seem "young?"
Regardless, this is dysfunctional behavior of this woman.
When I was in college, and living with my parents at the time, a similar thing happened to me... I broke up with the guy....he was very possessive etc., and I cut it off. But, no, I did not love him....as I saw how dysfunctional he was, and that kept me in reality. He KEPT on calling... well, I told my Father, he picked up the phone, and told him off... he said that if he continues to "harass" his daughter that he will call the police and file a report AND get a restraining order.
Well, that was that. Never did the guy bother me again. Mind you, it was scary... he kept calling, and following me, and was highly jealous etc. Dysfunctional and "potentially" it could have escalated. I had to have my guy friends with me when I went out... so that I would be "protected" so to speak. But yes, once my Dad told him off and said the word "police" and "restraining order"... this guy stopped harassing me.
If your son is youngish (or not) .. and obviously still in your home... this woman is posing a problem for you and your home as well. This is just VERY "threatening" and un-nerving. You CAN do something about it. It is not right... this woman sounds a bit off.... this is not "normal" behavior.
Your son, he has to SEE this. No human should have to go through this. He is being harassed etc.
This woman should NOT under any circumstances be a "wife to be..." What a mistake. Love has nothing to do with it... your son has to see that t his woman is a PROBLEM, mentally.
I wish you all the best... really. You and your Son MUST do something about this. It is in your hands... you can take control of this... do not "let" this woman CONTROL your son... and your home... and your phone... and your privacy.. and your sanity... and your well-being... and your mental health... and potentially your "SAFETY."
Do NOT allow it.
Your son must NOT be a "victim" to her, to this, to this problem. Nor you.
Take care,
Susan