CR001 wrote:Please remember that she cannot be seen as 'living in the UK' on a visitor visa. She should not be spending more time here than in her home country. Also note that she is not entitled to any NHS service for free.
If the ECO were to feel that she is using the visit visa to stay in the UK, irrespective of the amount of time spent in the UK, your mother can have difficulty in getting another visit visa in the future.
A visit visa can be denied if the ECO is of the opinion that the applicant is unlikely to return home when the visa expires. If the applicant stays repeatedly to the full extent of the visa and applies repeatedly for such a visa, that can be interpreted as a way to stay in the UK.
If she were to use NHS services, she will be billed at 150% cost and she may be refused another visitor visa until that bill is paid off.