Dog poo in common area

We live in a new apartment block, which is pet friendly. No worries there. Last Saturday morning, however, I opened the front door and walked 5 metres to the lift, where I found a fresh, steaming, neatly curled number 2 on the carpet. Myself and some other tenants politely asked the dog owner to clean it up, which she did, however there is now a dog poo stain (and wee stain near our front door) on the lovely carpet.  I knocked on her door and asked if she could have the carpet professionally cleaned or rent one of those special vacuum cleaners, to which she replied, ” But I'm looking after the dog for a friend.”

“Still,” I said, ” it's your responsibility to do it.”

“I'll see what I can do,” she replied.

She's a nice girl but still nothing has been done and we have to/need to walk around the stains every time. If it was just a food stain or something like that, we wouldn't mind so much.