As cris r says, it could well be kidney problems, especially as she is quite an old dog. I don't think the amount of times she wees is necessary relevant to kidney problems.
It can also be caused by liver problems, cystitis or diabetes, amongst other things (including a change to dried food or just simply hot weather).
hi
my dog started drinking a lot and ended up getting 10 teeth out which stopped the problem! she was 5 years old so get the vet to check the dogs teeth first!