My observations for your DD would be:
Think about the track record of the various schemes. Are they longstanding? I flag this as longstanding schemes are more likely to have local managers and central HR functions familiar with how to settle in, manage and progress school leaver apprentices. The website Ratemyapprenticeship can also provide a bit of a feel for this.
Longstanding schemes are more likely to offer evidence that school leavers do genuinely climb the corporate ladder in the same way as graduates. This latter point is definitely worth probing in relation to the PwC offer as the Junior Management Consultant role is a much more recent creation than, say, their equivalent accountancy apprenticeships.
In addition, clarify whether you are being offered degree level (ie L6-7) from the outset or L4 'with the possibility of progression to L7' (which might depend on future recruitment reqs as much as exam passes). The PwC offer sounds like it is more the latter; equally, the KPMG audit route, for example, is actually AAT, then the ACA, so is that being offered as a continuous pathway from the outset?
Think about how niche or otherwise the career is likely to be and where, across the country, other equivalent roles can be found as you progress in your career. The JPM centre in Bournemouth is huge (Dorset's largest employer) but the financial services cluster in Bournemouth is relatively modest in size. So it probably means sticking with JPM over the long term if you want to remain in Bournemouth and/or moving to London or to other niche locations with similar corporate banking back office functions. By contrast, the audit and consultancy routes potentially offer greater opportunities to adjust career path and location over time, if desired. They are all different roles so you need to be very clear about that too. Audit and back office FS opps are no everyone's cup of tea.
I have DC who moved away from home to take up school leaver schemes in different locations. They responded well to that challenge but you do need to have a plan and be mentally resilient. I would also say Bristol and, to a lessor extent, Bournemouth will be expensive. Manchester does allow for living at home initially and keeping connected to existing family and social networks.
All the above implies I am not being wholly positive about the PwC opportunity. This is not the case. If your DD got a good feel about the PwC corporate culture, then that is really important. The main thing would be to probe whether those going down the Junior Management Consultant route do genuinely push on and through. Even if things did not pan out, leaving after two years with a L4, having earned money and gained really interesting experience, would still allow for other paths to be followed. Your DD would still only be 20 then.