Student accommodation is often in the form of flats. So although you apply for a single room (en suite or not) you'll probably end up in a flat with others. DS3 is currently in a student flat in halls which has its own front door and comprises 8 single rooms and a shared kitchen. The rooms are all en suite, but there are similar flats with shared bathrooms. DS2 had a very similar arrangement a couple of years ago. Everyone gathers in the kitchen so plenty opportunity to socialise. There's probably some sort of communal area in catered flats too.
It's very common, as far as I can tell, to go out as a flat, and to make friends with other flats at least in the early stages.
It's also not uncommon to share with the same people in 2nd year. DS3 is going into a private flatshare next year with most of his current flat mates. DS2 did the same and, in his final year, is still sharing with one of his first year flat mates.
With that in mind, unless she really wants to save money, your dd might be better with a similar set up. She would have the privacy of a single room but also, unless she locks herself away, she will have lots of opportunity to interact with those around her. If she's going self catered she'll have to go into the kitchen if she wants to eat!
Your dd needs to remember that most people don't know anyone and are keen to make friends. We'd barely got DS2 into his first year room when his next door neighbour came knocking to introduce himself. Similarly, with DS3 people who'd arrived ahead of us were hovering wanting to help him bring his stuff in, make coffee etc.
I know exactly how your dd feels (I can remember being really upset before I went to uni because I was worried I wouldn't make friends). Wish I could nip back and give my 18 year old self a good talking to!