The best advice I can give you is don't had over money to agencies upfront
This. There is a huge industry of extracting money from prospective models for shiny portfolios that do nothing. A chap at work had his daughter recommended to an agency 'by someone at Vogue'... and ended up coughing up £1800 after a long hard sell. Even after chatting to me - and I know a little bit about the modelling industry - he was convinced that work would be forthcoming. Until it wasn't.
Take a look at
www.modelscams.org.uk
Reputable agencies won't want to see a shiny portfolio. They may charge something if they put one together themselves but will normally recover it from the payments for the first paying jobs.
If she's serious then the thing to do is start shlepping round the big agencies. I don't know much about agency work so we'll fast forward to how PurplePort et al works...
There are a vast number of hobbiest models working in the UK via PurplePort, ModelMayhem and a couple of other sites rather than agencies. Some have agencies too, but there's much hearsay that top agencies won't touch a model who's been anywhere near one of the internet modelling networking sites.
On PP models book directly with - mainly amateur - photographers. It's an interesting business full of the most extraordinarily creative people as well as a very small minority of dubious individuals, so be careful out there. PP's reference system attempts to keep everything as safe as possible.
Some models get popular & skilled enough to host studio days, or regularly get booked for workshops or group shoots. How old is your daughter? The great majority of the full time PurplePort based models I know do nude work - either 'artistic', glamour or both. Not that many pros make a good living doing purely non-nude work. That said plenty of hobbiest models work clothed.
If she goes down the PurplePort route then she should try to find a really skilled photographer to put a portfolio together. Be selective. You may find one willing to work in return for images that they can use for their own portfolio (aka TFI, time for images) if you cover hair & makeup costs - and possibly studio time.
Alternatively your daughter could find out whether she actually enjoys the job by finding a skilled local photographer with some experience of models and paying for a short shoot and a couple of images. Finding the balance between talent and price will be tricky. I'd guess that £300 should get her a basic portfolio together, but check all the terms of the contract before hand and make sure she gets rights to digital and print images. Really, though, she should be able to find someone willing to work for less via PP.
Then - if booking via PP rather than an agency - she should expect to work in return for images for a goodly while while she develops her skills - before she starts charging. Models seem to charge from £20-£50 / hour + travel (and there's a lot of travel) depending on experience. There aren't many at the top end.
Feel free to ask more specific questions if you think I can help.