score:3
If your mother does not have something to show for socio-professional, she can still submit documents on the strength of her social standing (i.e., the 'socio' part of socio-professional).
Examples would include, her marriage certificate, church/religious memberships, other memberships and affiliations that demonstrate an engagement with society. A reference from the family doctor might be helpful, but shouldn't be seen as required.
Since she is applying as part of a family group, it is unlikely to make a big difference either way. They are aware that not every applicant has formal credentials and as long as the primary is acceptable they will normally grant the dependant relatives a visa also.