Hi OP, I lost the majority of my sight 7 years ago so can offer some advice on the practicalities.
Your sister must see an ophthalmology consultant to be registered as SSI (Severely Sight Impaired/Blind).
She may possibly already be registered as SI (Sight Impaired) which is my current status. She needs to have a full conversation so she understands if there is any treatment for her condition.
TBH I'm horrified at the shoddy treatment she has received so far. She needs help and no professional appears to be guiding or advising her.
Once she has been given a Certificate if Visual Impairment it will open up financial doors to help your sister, including higher rate PIP on both levels which will give her just over £10,000 in support a year. This money is not means tested and can be spent on carers, cleaners, home adaptations etc etc.
When I lost my vision my local Sight Support team were really helpful with support and advice. I am also registered as Sight Impaired with my local council who offer support for home adaptations if needed.
I still work as Sight Impairment is a protected characteristic so my employers were happy to make reasonable adjustments for me.
Once again there is financial help available from the DWP via "Access to Work" which often means people get to stay in employment. I receive help with taxi fares to and from work and my employers received help with computer talking software and huge desktop maghifiers.
More importantly your sister will need a lot of emotional help. Honestly, when my sight went I cried every day for months - I'd gone from leading a normal life, driving a car etc etc to being dependent upon others for most things. Gradually I adjusted and I now lead a busy life with support from others.
My heart goes out to your sister but she needs to get the practicalities sorted (such as the Certificate of Visual Impairment) which will then open other doors of practical, emotional and financial support to her.
Most eye hospitals have an ECLO (Eye Clinic Liaison Officer) who is there to offer support to patients like your sister.
There are also charity websites out there such as https://www.bemyeyes.com/ which your sister may find helpful.
xx