How do i save my friendships?

I just started college and the rate of meeting interesting people has sky rocketed, but there are a few people who i truly feel are my long lost friends. on specifically is my new best friend, and she and i have connected from the beginning of the first semester.

I am also cool with her boyfriend, he is an upperclassmen who has helped me out with a lot of common freshmen problems along the way, so i really respect him

recently i noticed that he started getting a tad territorial by saying a few remarks to her disguised as jokes, which i know are coming from truth but i don’t want to say anything

i decided that i’m going to tone down how close me and my friend are because i know that he would never understand.
and i really don’t want to be a home wrecker because she is happy, so for the sake of their relationship i’m willing to put ours on the line

what are your thoughts?