I'm not even sure she was being rude about bringing up the flex time policy. If it was someone you didn't know well then no - I wouldn't say that but this was a friend and most people are more open and less guarded with their friends.
To me it falls under "interesting assumptions". I work at a flex-time company. I can still have a personal policy of always working til 5 for any number of reasons. Kindly don't assume that I'm either ignorant of company rules or that I'm unable to have a open conversation with my supervisor.
I didn't get the impression she was assuming that at all....but neither of us was there to get the nuances of the conversation. It would have been rude if she harped on it....but it was a little exchange in which the OP ultimately respected Carrie's policy of working straight through until 5:00.
I just don't see the harm in asking as long as you know when to back off. I also work for the Public Service and have flex time. I understand people choose their preferred hours and normally stick to them but that the flexibility is there when you need it.
At any rate the OP wasn't asking about whether her exchange regarding flex time was rude - it's done and over with and presumably no hard feelings about it.
I think that's where I'm falling under too. If the OP had continued to harp on the flextime, I think that would have been rude. But I've had conversations with coworkers at flex time where I've said "It's so nice to get out of here at 5, because I come in at 8 & it's so nice to do that with the flex time". & then they say "gee, I wish I could do that, but Boss won't let us" and I say "Boss can't *not* let you without a good reason" & they say "no, Boss doesn't like flextime, and said that they can choose to not let us work flextime, since it's up to each supervisor to decide that policy
", and that last italicized part is totally untrue. According to company rules, Boss HAS to evaluate any request for flex time and can only veto (or modify it) if there is a good, supportable reason. AND, a good reason isn't "Boss likes to have people here at 9am" or even "Boss wants a certain meeting to be at 9am every day, so everybody has to be there at 9, so no flextime later than 9 can happen".
I'm imaging that the OP wanted Carrie to know that Boss can't do that, since some bosses do lie about it. But once Carrie shut that down, then I think it'd been rude to continue, which the OP didn't.
I also think, in the case of the OP agreeing & then changing her mind...I've definitely initially said yes to something before I did the mental math. It sounds like OP likes Carrie enough to jump at the chance to hang out a little, but upon doing that mental math, it's just not really workable, and kind stressful to rush from one place to the next. How much talking & drinking could you really do in 10 minutes?