I actually work for a university, and I've spoken to many parents and kids with similar concerns.
Don't panic: most students don't aspire to a 'D' grade but two As is fantastic and I am certain she will be able to access most English courses in the country.
Universities publish entry requirements based on predictions, but as the year goes on the situation can change. Currently the trend at most universities is for published entry requirements to go down, but also for universities to confirm places for students who achieve lower grades than were either published or predicted. As others have mentioned, universities have attempted to grow with more places available but fewer 18 year olds.
Russell Group doesn't necessarily mean the best. Many universities outside the Russell Group have invested well and raised standards above even those older institutions.
My advice is that she carefully consider what she considers a 'good' university, she actually has a huge number of options. Rankings are a tool, but they aren't perfect. I can think of some cases where some long standing very high ranked institutions have received bad ratings in the Teaching Excellence Framework or complaints that undergraduates felt like fodder where being taught by PhD students.
In reality, what takes place in lectures and seminars at a university ranked say 20 and one ranked 40 might be the same. In a different table with different metrics they could swap!
I recommend she looks carefully at the modules offered and the structure of the course. For example, some universities make teaching the entire works of Shakespeare compulsory, which won't necessarily be for everyone! It's also worth checking what research centres they have and what they specialise in.
Does she want to do a joint honours? English and subjects such as Creative Writing, Journalism or Film are popular, especially if she's struggling to make up her mind. This is a very personal decision but I don't recommend Film as a Single Honours to students unless they are 100% committed to a career in Film and very driven, such as making films or writing about it already in their spare time. Not everyone may agree with this, but I think an English Lit degree has more transferability than a Film degree.
She also needs to consider accommodation: will she be guaranteed a university room? How much will it be? Will she need to take public transport to lectures? What's the average cost of living? What kind of part time jobs are there?
She also needs to think about location, such as, does she want to be in a major city or a campus? What student societies are there? I always recommend visiting and getting a 'feel' for the environment. Any university that makes her an offer will invite her to some kind of post-application Open Day (different universities may call them different things).
When it comes to her 5 choices on UCAS I'd recommend 3-4 that are ticking the right boxes for her with high requirements and 1-2 options which are solid choices but lower published entry requirements. Then, when the offers come in, go and see them and see which one becomes her first choice, and pick a lower offer as her insurance choice.