Female puppy's urine sometimes has slimy texture

[Amelia.]

My parents have just recently bought a new puppy, and all of us are inexperienced, so I'm not sure what I should do.
When she was no longer croutching down after peeing, I saw that it was this sort of slimy substance, so I patted her dry. The next time however, her urine seemed normal. This has happened twice this week, but all other times her urine is normal. What's going on?