Going by the questions (is someone allowed to go home, are they very strict) it sounds like there may be a bit of a misconception about the nature of university.
Your DD will be treated as an adult while at Oxford. If she wishes to go home every evening, let alone every weekend, she’s absolutely entitled to - it’s not boarding school and there are no curfews.
When I think of rules and regulations I think of ‘this is what must be worn, this is when you must attend breakfast, absence will be punished, doing this will get you a detention.’ Your DD is going to find precious little of that. Rules and regulations at university will encompass the big things like ‘do not plagiarise, don’t cause criminal damage’. In that aspect Oxford will be the same as any other institution.
For gossip and cliqueyness, if you’re thinking of ‘Mean Girls’ style cabals, not so much. Everyone rubs along, and naturally there will be friendship groups that form, but I didn’t find it especially tribal - some people you gravitate towards, others you don’t. There will be gossip. That’s what happens when you have horny young adults living in close proximity. It’s rarely malicious, but it’s inevitable.
Workload is heavy, especially compared to other universities. For an arts student, two essays a week to be written and discussed/defended in your tutorial, plus in some cases a handful of classes (lectures tend not to be compulsory - again, you’re an adult, you’re only hurting yourself if you elect not to attend something that’s going to help you.) Not sure what else lawyers have to do, I seem to recall moots being a thing. Reading lists are long, so you quickly acclimatise to scanning for the nuggets rather than trying to digest whole chapters of each book.
In terms of pressure, I found it was really all internal. No one is cracking a whip and saying pull your socks up - if your essay is at a 2:2 level, that’s the feedback you will get, but there won’t be any ‘see me after class’ notes for you. Some colleges have reputations for producing exceptional students, so the culture there may feel a little pressured, just in terms of being among high-achieving cohorts.
Pembroke and Oriel have very strong rowing traditions, and Keble is right next to the University Parks, which are lovely. Pembroke will also claim to have the best kebab van outside their college, but that is pish, I wouldn’t listen to that. And that’s about all I know about the colleges I’m afraid!