Hi Theresa! I am soo sorry to hear that about your other daughter.
Sounds very similar to my experience. I would take her back to the GP and request an ultrasound. I had mine the other day and as far as the sonographer could tell it was all clear. What was reassuring too though, was that although it doesn't provide a view of the appendix, they can tell if there is any free fluid in the pelvic area due to a problem with it, so I would highly recommend going back. I just wish I had done mine sooner so that I could have had a diffinitive 'yes it is a cyst' or 'no its...'!! >
Let me know how your daughter gets on, and my thoughts are with her, it is absolute agony and stressful not knowing what is going on.
Vicky xx