my girlfriend (22F) is going to “stay at her friend’s(23M) house tonight” and I (22M) am unsure how I feel about it

My girlfriend and I (18mo relationship) both live in dorms for college. I have four suite mates/room mates and she has two. Her and her boy friend have been friends since “before she was 12” (pretty sure they also dated briefly in middle school; she told me that) and her friend just got a new apartment (within the last few months). <br><br>We live about 20min car ride apart, which is why my gf usually spends weekends at my place (the only people that live in the suite are me and one of my friends). <br><br>I never had any issues with her friend until they decided to have an impromptu 2hr conversation face to face last night while my gf was over, and she was wearing nothing under my tshirt (no boxers, no panties). I did not say anything, as they were talking about their lives (she was apparently having a rough day) and I just went to the next room. I did text her about it (after they were done talking) saying that it mad me uncomfortable and she “has never done that in front of [him] before.”<br><br>Anyways, she usually drives home on Sundays (to get home before classes on Monday) but told me tonight that she is going to stay at her boy friend’s place because she doesn’t “feel like driving at night.” She also drives a Honda Type R and spends a lot of time at the track so I don’t think that’s the real reason. <br><br>I told her I was okay with it, but I am actually unsure. I’ve never had problems with her friend (and trust her) but the fact that they had a 2hr conversation face to face last night when she was wearing nothing under my shirt really bugged me idk what to think.<br><br>Also, when she said she was going to be staying with her friend tonight, I told her I was okay with it, but wanted to make it clear I only “trust her, not her friend.” <br><br>Any thoughts on this? (Sorry if the post is kind of hard to follow)