Ah ok!
So, buy a doorstop for her room. It'll help her be socialable in the early days to keep the door open and chat to her flatmates.
If she hasn't already, get her to join the Facebook / WhatsApp groups for her halls. My DD is still friends with some of the people she chatted to before she started. She bumped into a couple of them on her first day and from day dot she felt she knew people.
Buy tickets for the freshers events asap - they sell out quick (way before term started fir my DD)
Give her something to put in the flat kitchen to share in the first few days. It's a great way to get to know flatmates. One of my DDs flatmates baked brownies. That went down a treat.
Take a favourite board/card/drinking game so they can get to know each other in the early days
Get your DDs postal address early so you can send your DD a nice treat (cookies etc) to share with friends when she's feeling homesick in the first few weeks
If your daughter is shy and struggles to get to know people, then get her to identify those she thinks she would like (from the WhatsApp group chat) and get her to ask them what they're taking to uni. They all seem to love discussing what they think they need. My daughter spent hours discussing that with people last year.
Pack enough plates so that she can entertain others. One plate etc is not enough!
And remind her to balance work and partying. The uni will not tell her she is failing if she is getting the balance wrong, and unfortunately I've seen too many people have to resit their first years because they didn't get that balance right.
But most importantly, tell her she only gets one shot at uni, so make the most of her three years there. Get involved, have fun and work hard.
And for you, yes you'll miss her, but soon it'll be more than normal. Whilst I've loved having my DD home this summer, I can't wait for her to go back to uni next week!!