DD (24) has a Marc Jacobs camera bag - they are a bit of a 'classic' and hers always gets admired. They're more expensive but you might get lucky and find one on sale (I did when I bought it for her!). She's a huge fashionista so trust me, if she loves it you should be ok!! There's a lot of copies of this bag out there so if she's not into her designers, that might be an option.
My girls only have 'designer' bags (not mega expensive, not Prada level!!) - and yes, I know I have created monsters!
Alternatively try discount shopping sites like Brandalley, Zalando Lounge, Yoox - though it might be too late to order online if her birthday is soon. Brands like Michael Kors, Paul Costello, etc often have bags reduced to half price depending on the season.
My 20-somethings raved over a Kurt Geiger back when we were on holiday and so both of them bought one. They were jewel colours with those chain handles that are all in right now. Don't see them on the website currently but again you might pick them up online somewhere as they were reduced in the summer sale.
Do not under any circumstances get her Radley - she will never forgive you lol!! They are an old lady bag - I'm probably considered to be an old lady and I wouldn't buy one either!!
There are usually a lot of Guess options but I think they are a bit ubiquitous. MK has kind of gone the same way. Fossil do some decent bags but having said that, neither of my DDs has one.
Get your DS to suss out what she likes - maybe they could have a wander in the shops and he could get an idea what her taste is.
She's a lucky girl!