Any recommendations for pee repellent spray for brand new rug?

A friend wants to take precaution and make sure my dog wont pee on her brand new livingroom rug since my dog peed ONCE on the mat in her foyer. (Dog is 12 yrs old and rarely pees inside, not sure what happened that particular day.)

Im asking for recs since most repellent sprays are marketed as odor/urine/stain destroyers and wondering if they will work as a repellent for a rug that she has never peed on? Thanks in advance!

Update: I've relayed a few of your comments to her and she wants my dog to wear a diaper. Am I wrong for rejecting and being upset at that idea? I mention this because id like to hear from fellow dog parents. (My friend has never had a pet, loves them but doesn't like the responsibilities of having one.)

When we visit, I take my dog out to pee 3x a day, something she has gotten use to ever since newly becoming apt dwellers. (Dog had yard for 11 years) I understand wanting to care for your new rug but my dog is not gonna be comfortable wearing a diaper. I offered to just not bring her over because I can't control or guarantee any of my dog's actions...or anything for that matter but she likes having my dog over. My dog is very well-trained and mostly just sleeps when she's there. I wouldn't take her places if she was a problem....but she DID pee that ONE time.

Would you be ok with making your dog wear a diaper only when visiting a specific home?