my 3 month puppy has a white stringing discharge when she urinates
Hi
A certain amount of mucus is normal, especially in the period preceding the first 'heat cycle' or 'season'.
However, if your pup seems to need to urinate very frequently, licks at her genitals a lot, or seems uncomfortable or unwell in any way then I'd suggest that you have your vet take a look at her to make sure there's not a problem.
Best of luck.