> i dont know if they mum was tested as i never met the people who owened her,
Your best bet is to look up all the health issues that Border Collies can get, and assume the mum wasn't tested. Some issues are passed on in a random way (epilepsy for instance) while others are recessive genes, meaning for your dog to suffer from them, her sire (whatever breed he was) must have carried them as well. So by knowing what issues *can* affect BCs then if her father (whatever breed) carried the same genes, you have a risk - if not then it's unlikely. Eye issues are likely to be the main thing, such as PRA and cataracts, since so many other breeds share these same problems.
But you may be perfectly lucky and she turns out to be very healthy, only suffering ailments in her old age that any breeds can get..... such as cancer, age-related loss of eyesight, or age-related heart or circulatory issues. We all have to die of something! ;)