Admissions Officer for pre-reg Nursing here, apologies in advance for the long post (!)
There is no NMC requirement for 5 GCSEs, so what is required here varies considerably by institution. If institutions say 5 GCSEs in their published standard entry requirements, this doesn't necessarily mean that they will insist upon them.
However, they will insist upon GCSE English & Maths C/4 or above or acceptable alternatives. This is the standard threshold set in response to the NMC requirement that institutions 'confirm on entry to the programme that students... have capability to develop numeracy skills required to meet programme outcomes' and 'have capability in literacy to meet programme outcomes'. Acceptable alternatives vary by institution and can include Functional Skills Level English & Maths and various other Level 2 qualifications.
So, please check with individual institutions about GCSEs - look at their webpages, go to Open Days, phone up Admissions Offices / Nursing Admissions Tutors etc.
As competition for Children's Nursing places is very high at most institutions, I would encourage her to gain care/healthcare experience and do thorough research into the profession (relevant literature etc). If she draws upon this well, this will enable her to evidence transferable skills, motivation, insight and commitment in her personal statement and if shortlisted to interview.
She also needs to ensure she is on track to meet the grades / UCAS points requirements - she should approach individual institutions now to investigate these before she makes her Level 3 choices. We accept a wide range of qualifications, but the most common are BTEC Extended Diploma Health & Social Care, 3 A Levels or Access to Higher Education Diploma in a relevant subject. Typical offers in my region vary from BCC to ABB at A Level (104-128 UCAS points) or DDM/DMM (112/128 UCAS points) in BTEC Extended Diploma.
Some institutions nationwide might accept her with an apprenticeship, but we and all the institutions in my region would not due to lack of UCAS points. If she applied with an apprenticeship in Health & Social Care, we would refer her to our Foundation course so she gets the academic grounding, and then encourage her to re-apply the following year.
People talking about Nursing Associate apprenticeships - Nursing Associate Foundation Degree graduates can enter 2nd year of an Adult Nursing degree, but not Children's as far as I am aware. This is due to the children-specific content covered in Year 1 of a Children's Nursing degree, so it would be two years apprenticeship + three year degree. Most apprenticeship places go to existing, experienced employees. She would need GCSE English & Maths at C/4 or above or acceptable alternative for a Nursing Associate apprenticeship.
You could investigate universities that offer the Nursing Degree Apprenticeship (a very small number offer this in Children's Nursing). However, all the ones I'm familiar with have the same entry requirements as a standard Children's Nursing degree.
So, in summary, contact institutions she's interested in to check their specific requirements, and try to come up with a plan with the college that enables her to meet those. Also ask what other things are not required but will strengthen her application and about their selection criteria when assessing personal statements/at interview (may be best to ask the Admissions Tutor rather than Admissions Office this question and either face-to-face or over the phone as they tend to go into more detail that way.)
I wish her all the best with her future application and if you have any more specific questions, please PM me.