The best thing you can do about this is to ignore it. This sort of behaviour actually arises from over-excitement, and the dog feeling intimidated. It is known as "submissive peeing".
The good news is that it is most common in puppies and adolescents (around your girl's age) - and just about every dog grows out of it.
If you know you have people coming over, then it is a good idea to take your pup outside shortly before they arrive to empty her bladder. Or if necessary, you could take her - without making any fuss about it - at the time they arrive.
Beyond that though, the best thing to do is to ignore the dog and ask your guests to also ignore the dog. Let her calm herself down before anyone takes any notice of her, and you're far less likely to have an accident. That sort of 'ignoring' will also help her to get over her excitement/fear faster, and grow out of the behaviour altogether.