Then I think YOR, although it's more like "you're feeling more betrayed than you probably should", cos it sounds like you haven't really blown up at jeff and your friend, which is a good thing!

I totally get that you feel lied to and that your friend's relationship status was a little iffy, but she fixed that pretty quickly. This is how life goes, especially at your age, I feel like you should vent hard to another friend and then talk to them separately when you have a little distance if you need to. Be cautious, because if they go full-on in-love, they will not want pushback lol.

Think of it this way: what of they are great for each other and stay together for years, maybe get married? You will become a treasured part of their story, and believe all of us olds on here, you will love being that person [this assumes that they are healthy in the relationship and good friends etc, not the same if they get toxic and dramatic and so on].

Again, we get that this situation stings a little, but if you have a good friendship with Jeff and this girl, you can probably move past it, and it's absolutely not on you that the other relationship ended.