The more I look at these EU matters the more I realise that they are quite complicated.
You mention "a stay-at-home mother" and if she has never worked in the UK then it might be different, but in the document you referred to, at 6.2.1.2 it makes clear that :-
"Worker" includes:
- job seekers
- those between jobs (for example, women who have ceased employment on becoming pregnant but who intend to resume work at some point after the birth)
- those undergoing training in their own or another field
- sick, injured and retired workers
:- which is clearly far wider than those who are actually in employment.
For example, if an EEA Citizen comes to the UK and starts their married life in the UK, initially having an employment, but then they stop working to have their family, intending eventually to resume employment, maybe many years later, after the children have reached sufficient age, then it seems to me that throughout the time in the UK they will have been within the definition of "worker".
Which just leaves someone who comes to the UK and never works here, and indeed never seeks work here. I shall look further into that aspect.