Choices & open days:
She should start thinking about this in Y12 as the open days are usually in June, July, September & October.
For the course she wants to do, make a list of the universities that offer it and for each one, find out the typical grade offer.
By the end of Y12 she should have some idea of what grades she is aiming for - look at universities at this level, just above and just below (for insurance).
If the list is too long, she can reduce it using other criteria. Does she want to be in a big city? An easy train journey from home? If it's a course that varies a lot between universities, she should look at the course structure (on the university website).
Once she has a shortlist, she can start planning & booking open days.
Applications: this is done in the autumn/winter of Y13. She needs to draft and write a personal statement about why she wants to study that particular course (see UCAS website for guidance on how to do this). There's a big online form. She fills in her personal info, her GCSE grades, a list of five universities/courses she wants to apply to and her personal statement, then her school/college adds predicted grades and references.
Offers
She should start receiving offers in the spring of Y13. Each offer will be conditional (certain grades needed) or unconditional. She needs to accept an offer (and can also accept an insurance or back-up offer) by the first week in May.
Finance
Once she has accepted her offer(s) she can apply for student finance.
The student loan comes in two parts. One part pays for the tuition fees. The other part is a maintenance loan, for accommodation and living expenses.
The amount of maintenance loan she's eligible for will depend on several things, including whether she'll be living at home, whether she'll be studying in London, and the income of her parents. The basic maintenance loan is £4000ish a year for students whose parents earn over £60K, and more for those whose parents earn less than that.
Student Finance has an online tool where you can put in information and it will estimate how much she'll receive.