The OP doesn't have to spell out her financial situation to her daughter in detail. She could just say, for example, that, apart from their state pension they only have a small occupational pension and that doesn't allow for unexpected expenses like this, especially at the moment when petrol is so expensive and inflation is around 10%.
Her daughter can easily find out what the basic state pension is for herself, and whether that is exactly what they get or not doesn't really matter. it should be enough for her to realise her parent's circumstances.
I would have thought any thoughtful or observant daughter would know roughly what their financial situation was without being told.
I never knew what my parent's retirement income was, nor did I want to, but if I had been asked, I could, after some thought, have hazarded a reasonably accurate figure because I knew what occupational pensions they had on top of their state pension and how long they had worked for the relevant employer.