Some of my cousins used to model, so this info is a bout 20 years old:
Once you have the professional book, you need to be close to where the cattle calls (castings) are, or be able to travel. Agencies will drop her if she can't make the appointments, and there are LOTS, sometimes several a day, when you're trying to land your first jobs. This is where living in major cities where the shoots and castings for things are done is handy.
Don't let anyone scam you into paying for anything, classes etc, just pay photographers for their shoots. Yes, your own photos can get her into the agency (or not, don't pay for shoots up front to approach agency, just show her in a good enough light, they'll know if she could model by that), but if they take her, or say they might, the agency will tell you to pay for professional photos after that. If they are interest in her, they will give her a list of photographers. If she is so drop dead knock out gorgeous that she was scouted waiting tables in the boonies, the agency might pay for the shoots. But if you're approaching them, like most people, you'll most likely have to pay for the shoots to make a book worthy of going to their job appointments, so don't be discouraged. Once she gets a few jobs, she can use those photos and her book will grow from there without you paying.
Depending on where you live, the travel can get pretty expensive to get to castings. Now, this was before everything was done on the internet, not sure if agencies book jobs from emailing photos alone now, but if so, there is even more competition, so I'm sure there will still be in person castings involved.
Tips: Usually the casting people are looking for a very specific type for their job, which is why tons of appointments end in disappointment at first. There is nothing you can do to sway them if she's blond and they want a brunette (hopefully the agency is good at screening, or the casting people have weeded through emailed images already and narrowed it down), but it really will help in the beginning for your daughter to be professional, well groomed, confident, good at walking, great posture, and nice. Sure, once she's "in demand" she can be a raving, slouching b__tch and show up hungover with zits to jobs, but in the beginning her impression in person matters when no one knows her pictures yet. They do care if she seems dynamic and nice to work with if another girl there for the job who is "similar and just as pretty" seems more annoying.
Don't lie on her stats! Don't say she's 5'11 and 84 pounds if she's a normal healthy size thinking she could quickly dump 10 pounds if she gets hired. The casting will dump her when they meet her. But she may get the job for the healthy catalog shoot instead of the runway show with her real stats. Honesty pays.
Also, keep the first photos simple and natural. Elaborate styling cold work against her.