clippityclop
I'm in secondary, but the impression I get is that primary workload is higher in some respects.
It's all anecdotal, but here are some differences I've noticed between my experiences (range of secondary schools) and friends/colleagues in primary:
Greater independence for students at secondary (eg. It's reasonable to get an hour silent working at secondary whereas LKS2 and under it's less likely)
It's more accepted that differentiation can be done via support and questions etc in secondary, whereas friends in primary seem to be expected to do 3 or 4 tiered tasks for every lesson for different tables
Marking load seems to be more flexible in secondary (e.g. 2 assessments a half term / one deep marked piece a cycle), whereas primary friends seem to have to mark maths/English daily.
Secondary seem to be more open to alternative models of feedback, whereas friends in primary have had to print off labels with objectives and highlight them in school colours, or write written comments to 5 year olds who can't read.
I know workload isn't a competition and both are tough in different ways, but I get the impression that primary workload tends to be higher (or at the very least seems to comprise of things that would put me off).
Of course, a primary teacher might look at secondary pastoral loads with a tricky form as being worse and more onerous than their daily marking, or might find the expectation of turning lots of a level essays round to be worse than planning tiered activities.
In terms of advice, it's a case of going in with her eyes open. Once on her training year, avoid getting drawn into the odd competitive world of who works most, whose mentor thinks they're outstanding after 10 minutes, moaning about placements etc. Mindset and approach makes a massive difference in your training year.
For her NQT year, try to get the best school she can, whilst being aware that best to work in doesn't always mean best Ofsted or highest results.