I think professional advice if you can afford it. CAB can be hugely helpful, but they are rather overwhelmed and you may have to wait.
However, in the spirit of this board - the main 'claim' on her part will be what she has missed out on, for whatever reason. Your pension won't usually come into it, but your general circumstances might.
Example:
Woman helps man to build up a successful career, maybe by working unpaid in his business, maybe by giving up her work to concentrate on the child whilst he worked long hours or studied. At the end of her working life she has a 'pension gap' from the years she didn't contribute - specifically because of their relationship at the time. He has a very good pension because of the boost she gave his earnings.
If something like this is the case, it should have been sorted out ages ago.
My mother told me to make sure that I had my own pension. Because my OH worked long and irregular hours, I stopped work for a few years when the children were young, and asked him to pay into a pension for me to cover those years.