What is the best phonetic app for the iPad?
This is a little left field from the answers you requested, but I would suggest turning on the feature to allow screen reading in the accessibility settings area, which allows any app that uses a standard text area that can be cut/paste to be read aloud.  In this way as she encounters test in any app, she can have portions of it read to her, and the diction is pretty good as a rule, allowing her to learn by real world example.