It sounds like to me that Abby is just being a typical toddler. She's going to go through phases where she refuses to eat certain foods. If you are having a difficult time getting Abby's daily phe intake in each day you could try adding regular milk or powdered milk into her formula. One ounce of regular milk is 50 mg of phe, and one gram of dry powdered milk is 17 mg of phe.
If you are looking for support groups macpad.org might help (http://macpad.org/page.aspx?id=92188). They have a list of support groups for PKU throughout the US. It might be helpful to contact the president of either Western or Eastern support groups depending on where you live.
Utilize your clinic. They are there to help you, and from what I have heard Children's Hospital of Philidelphia is a great clinic.