Oh my goodness...this one stumped me completely!! But, please don't use suppositories on your little girl. It would appear that her poop is okay, and this could make her very uncomfortable since it sounds like she is experiencing discomfort in her lower region anyway. Yikes! Not to mention they should only be used when under the care of a physician.
I have to agree with the first poster, on some level your little girl already knows she doesn't like the feeling of poop. She can feel it coming, and is distressed by it...terribly, but yes distressed. My sister was such a girlie girl as a little girl she would not cry but yell, 'it's dirty, it's dirty'...and, nobody had told her it was dirty or gross. She just knew.
If her tummy isn't distended, and she's fine afterward then I would go with that theory.
On the flipside, if you are truly worried and need that opinion of the pedi, then make an appointment and have her checked out. It doesn't hurt...really what are they their for???
Good Luck and keep up the great job.