Answer:
Letter writing.
Step-by-step explanation:
Dear Mary,
I know you don't like talking about the issues regarding our relationship. But as I have observed and seen so many times, I think it's only natural that I frankly tell you the truth so that there won't be any misunderstanding between us.
As lovers, it is natural to feel jealous and also be possessive about someone you love. But your jealousy is a bit too extreme. There is nothing happening between me and the other girls. I am just an open person that everyone feels comfortable around, and that's just who I am. So, whenever you see me around other girls and having a good time doesn't mean I am flirting with them. They all know (and I do make sure they know) that I am dating you. So, rest assured, I am wholly yours.
So please, stop stressing yourself and making yourself depressed or even angry. I am yours and yours alone. I love you with all my heart.
Lots and lots of love,
Jason.