My friend told me that my bf will cheat by next year since he's three years younger than me

Hows that friend able to predict that? Jealousy or something else.?

"friend" really?

Define "friend."

Maybe that happened to them or someone they know and they assume it'll happen to you, because they're jaded

That’s no friend. I would guess it’s probably jealousy. In any case, she doesn’t wish you well.

Hard to see your friend (friend?) as a reliable judge of anyone if his/her supposed " evidence" is no more than a rather unimportant difference in age...

Wth does him being three years younger than you have to do with his ability to not cheat???

Sounds like a challenge

Unless your friend is a psychic I wouldn't worry about that bridge til I have to cross it.

She knows bc shes gonna fuck him

Doesn’t sound like a friend to me.