That is something called submissive urination or excitement urination. She is (in doggie language) saying, "You're the boss. you're the boss. You're wonderful. I'm so glad you're home. I'll do anything for you. And I'll prove it by peeing right now. See? I think you're the greatest." That's what they do when they're in a very subordinate position in the family. There is nothing to do. Never scold for this or react because it will just make the dog all the more submissive and pee all the more. If you put some kind of diaper or something on the dog at times where she's most likely to do that, that might help. Otherwise, most pups will grow out of it.
Confidence building games and obedience training, using positive methods will help build up her confidence level. That can help get her out of this as she matures. Look up online for confidence games for dogs. Or for submissive dogs. Tug of war where she wins is a good one. Just make sure she is willing to give the thing back to you when you ask. You can trade for a treat.
You can even do a search online for submissive urination in dogs. Then you might get some more info. Good luck.
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