VERY fearful longhaired min. doxen... 10 months old

Question
I have a 10 month old pure-bred miniature doxen who I have had for about 6 months now. I got her from a very good breeder and she is very healthy. I am her owner. She and I have a very close bond and she follows me everywhere! she is so sweet to me (the most), my mother, and my sister. The problem comes in when I bring people over. She poops EVERYWHERE and will hide for hours until the guest is gone. When we take her to get groomed, she will shake uncontrollably and pee and poop everywhere because she is so terrified of people. She is OK with other dogs. We have a 12 year old basset beagle. She adores him, and they play every day. We have tried training her around other people, exposing her to new surroundings, and much more, but nothing works. I really don't think I did anything wrong to make her so scared of people. Please PLEASE HELP! I just want her to be more confident and I want people to see how sweet she really is.
WHat should i DO!!

Answer
If you got her from a breeder at the age of four months, then the breeder apparently didn't do much to socialize the dog, and, unfortunately, because the optimal socialization period is between the ages of 8 and 12 weeks, you missed the opportunity to do much of it yourself.  In my opinion, this is not responsible breeding!  There are two very good books that might help you understand how to work with the dog to make this a bit better, although it will probably never be as it could have been had you gotten her at an earlier age, or had your breeder exposed her to many different situations and people.  One is "The Cautious Canine" by Patricia McConnell.  The other is "Help for Your Shy Dog" by Deborah Wood.