Some kids are almost scared that some wierd foriegn thing is coming from there body. There is a book that talks about how everybody poops. so they understand that it is natural. Also, praise praise praise.. special treat only for when she is a big girl and poops on the potty.
my daughter was the same way. she didnt like anybody being around. we had to put her potty in her room and she would shut the door and do her business and then come get me when she was done. we also gave her raisinets after she went on the potty.