In terms of jobs, it depends on subject and the area she is applying in. Shortage subject in an area of the country with not many ITT courses- it's very likely she will have a job sorted by Easter.
If it's a less shortage subject and there's lots of competition, she could still be applying for jobs in the last half term of the year. Some people do find jobs after the May half term, especially as there's less competition from those already in post. So she might even still want to be interviewing during the time you're proposing she goes away.
Equally, if schools did want her to start in July, and she said she had a holiday booked, then she'd potentially lose out on two months of summer pay.
The thing with the PGCE is that you're also applying for jobs throughout, and that means that it can be hard to schedule things. In a way, I actually think Easter is safer- yes, she'll have work to do, but it will be easier to plan, and if it's just a one week holiday, then there will be another week to catch up with work. But on the other hand, she may well be knackered at this point in time.
How would you feel if, at the time of the holiday, she said she wasn't able to go away with you for reasons relating to her course/new job?