Re: can someone shed some light on this please?
Could be bladder cancer, but it also could be kidney stones, which can cause a lot of bleeding.
She needs to see her doctor ASAP and get tested for UTI and, if that's negative, she needs to see a urologist for a cystoscopy, which can detect bladder cancer and then, if that's also negative, she needs to see a nephrologist to rule out kidney stones. And yes, you can have kidney stones without having a lot of pain, if they're not passing through the ureters at the time.
But given that this is new, and she's never had it before, it needs to be thoroughly checked out.