In terms of having done a gap year to be more mature on arriving at uni, I don't entirely agree - I did a gap year and struggled at (Bristol) uni. The ability to socialise doesn't have much to do with maturity, imo - it's a knack some have, like sex appeal. Looking back, you'd have some hangers-on, just in the clique as a kind of mascot, they had nothing to say, no personality but were just accepted, though they'd feel threatened by any outsider. Still, they had the knack of having friends and I didn't. It's possible that having led in one's subject, you can feel like you're a leader when actually you're a mascot...
If anything, doing a gap year can make you more worldly and less tolerant or if you prefer appreciative of anyone with a limited outlook on life.
For practical advice, I'd suggest your daughter keep a look out for places she might want to switch to at the end of year one, simply as a kind of back up or form of surveillance, something arguably she should have done before going to Oxford but quite understandably didn't. I mean, to look around other places can be interesting, at the least - and some will/may be able to take her omitting year one, go straight into year 2 so no loss. I got offered one of these decades ago doing history at a uni or college in Twickenham but bottled it for all kinds of various reasons, and while things got better for me at Bristol it never really felt like the place I should have been at.
A recall a thread from a year back where someone disliked being at Exeter and then switched to Norwich which turned out to be friendlier. Of course, it's not right up there in terms of academia. It would be good in any case to get good grades at the end of her year so no one can say, oh she wasn't up to it.
So at the very least, she could phone around to see what her options are, and of course also throw herself into some of the suggestions for Oxford on this thread to see if it comes off.