<human>: Condense the text into a few key points

Honestly, I don't see this as too much of a problem, but there's some disagreement about this, so I'd like reddit to weigh in. 

A couple days ago, my girlfriend and I were talking about going back to school (she's starting junior year, I'm starting college) and she mentioned that she, her female best friend, and her ex were going to carpool together. She dated this guy over a year ago, for about two weeks, and decided he wasn't boyfriend material, so she broke up with him. They're still sort of friends (acquaintances, really), but they never really talk and have pretty much nothing in common. 

I have absolutely no problem with this, for a number of reasons. 1, our relationship is rock-solid and neither of us would dream of cheating on each other. 2, she and this guy dated very briefly a long time ago, and she's changed a lot since then. 3, one of her best friends will be riding with them as well. 4, the arrangement was with my GF and her friend, and then the ex asked if he could join them. 

A couple of my friends (who don't know any of the people involved) told me that I should be more worried about who she sees on a daily basis, though. I think they're insane and I have nothing to worry about, but I'd like to hear reddit's opinions on this.
<bot>: GF carpooling with friend and ex from a year ago, I'm not worried, friends say I should be.