British Overseas Citizen not a Indian Citizen nor a British

Hi,

I need help and advise for my mother's entry clearance. My mother was born in Nairobi and got British Overseas Citizen passport. She married to my father in India and stayed there. After my father's death she decided to renew her passport and we got it from Mumbai Office.

Now as I am living in UK (on HSMP) and she traveled to UK for the first time. Immigration officer at Heathrow allowed her six months entry clearance. Now I am confused as for her stay in India I have to pay her visa fees plus she can't be in UK for more than 6months in a year period.

Can anyone help me how to apply for her ILR / entry clearance in UK so that she doesn't have to take any visa permission from UK agency whenever she comes to UK?

I have contacted UK Home Office and Immigration control and they asked me to contact VFS in India and when I contacted various VFS centre in India they asked me to get it done thru UK Home office.

Much appreciate if someone can help me with my mother's case and I can get her ILR / entry clearance.

Thanks,