Wow! I love getting easy clients like this! We can tell that Grace is stimulable for /r/ because she was able to imitate my models. Picking out therapy targets for Grace is easy peasy. The letter /r/! I base my articulation therapy on a combination of motor-based approaches. Here's a quick outline: discrimination, isolation, syllables, words, phrases, sentences, reading, and then conversation. The idea being that practice should occur at increasing levels of complexity until a sound is generalized into conversation. Come back to follow me through these steps and gain ideas for each level.
Talk it up!