She needs to approach the housing team to make a homelessness application asap they will most likely have a duty of care.
If it is late in the day or at the end of the week, you can call the phone line to report a vulnerable person, and this will establish if she has a social worker.
Also – Shelter has a legal helpline that is open seven days a week, they will be able to confirm her legal rights and may be able to advise on what she should do on the day.
You can also look at https://www.gov.uk/civil-legal-advice
Her GP can refer to her council’s Housing team via the local council phone line. They will assess her for emergency accommodation through the local council; this consideration will be fast-tracked due to her health status.