How long have you had her?  She could be marking her new territory if she is new to your home.   Also have you put hay in her litterbox to entice her more?

To get the smell out put some vinegar on it or on a rag and rub the area  b4 she goes there again or your parents notice. 

How old is she?   Young ones under 4 months makes mistakes sometimes.   If she is older she may need  a spay that will help tremendously.

Also if you can catch her as she is putting her tail and hiney out to pee and put her in her box that would help too.   Takes a while to catch on to the posture just b4 a pee I know. 

When litterbox habits disappear, it’s a good idea to limit the space the bun has access to. You can achieve this by only allowing her to play in an xpen or in a NIC grid fenced area. Start very small, with a litterbox in the area and as she learns to return to the box, you can expand her space. Since she is new to your home, some of the behavior may be marking. Are there other animals in the house, or were there? Even if you had another pet a long while ago, she may be able to pick up on that scent in the carpeting. If it is marking, it should be short-lived until she grows accustomed to her surroundings. The best thing I have found for pee on the carpet is a white vinegar mixture.