I would note that, if she is doing anything linked to medicine she should check where she’ll be located as it is taught and researched all over Merseyside depending on the discipline.
As has been said, the Wavertree / Smithdown Road area is very studenty (undergraduate), whereas the Aigburth / St Micheals area is more ‘young professional’ housing which might suit her age better? South of Sefton around Mossley Hill is nice, semi-detached housing with gardens. Between Upper Parliament Street and Princes Park is a bit rough and as much as I love the city, I wouldn’t walk that route with a laptop bag or ride through Princes Park after dark, I would keep to the well lit streets that have plenty of traffic.
The city centre is very nice, but more expensive and more difficult for public transport to campus. The Canning Street / Anglican Cathedral area is lovely but I guess priced accordingly. If she’ll ride throughout the year, then the area just north of Dale Street (the traditional business district) is getting more studenty because of the number of John Moores students.
One thing you might notice is that one street can have a very different character from another. We lived in a cul-de-sac off Edge Lane and it was great, couldn’t have asked for a nicer place, but some other side streets were pretty rough. Especially to the north of Smithdown, one street can looked well looked after and be very friendly and the next has a nuisance family so have a good nosy around before she decides.