Hmm...
Does this involve the dog coming onto your property, ie, up your driveway.. does it involve the dog being off lead and/or unsupervised on a road?
If so, YANBU.
If your car is parked on the road and the dog is not entering your private property... and its on lead, then probably YABU - because it won't just be HER dog, her dog is weeing there because other dogs (and probably foxes and cats) also leave scent there.
Urine is sterile when it leaves the dogs body (or anyone elses), bacteria grow on it if its in a suitable environment which outdoors in the UK just isn't - are you letting your children grub around on the floor by your car wheels or front door much?
Whether you are being unreasonable or not, I would politely ask her to stop letting her dog pee by your front door at the very least, because it will soak into the brickwork and smell - car wheels and bushes I'd be less concerned about, as I say, other animals will also be scent marking these on a regular basis so stopping her dog won't make much odds.
Not that you asked but theres a fab product called Odor-kill that you can spray onto concrete flags/brickwork etc that gets rid of the wee and disinfects (do NOT use household bleach on it, it breaks down to ammonia, the same as wee does and thus attracts animals back to mark again).