A: "Mommy, how can you touch the planets?"
M: "Well, you have to fly a spaceship into space and land on the planets. It's a very long trip into outer space."
A: "Ah, right. You have to be a rocketgirl."
A: "How can I be something when I grow up?"
M: "Well...you can decide what you want to be and then go to school for that. If you want to be a nurse, you can go to nursing school; if you want to be a doctor, you can go to medical school, if you want to fly an airplane, you can go to school to become a pilot...(and on and on I went with lots of different options)"
A: "No, no, no...I don't want to do any of those things...I'm going to be a princess, a mermaid and then a cowgirl, like my Grandma Kathy
A: "...But you'll have to drive me to school for those things..."
A: "Mom, but how can a mermaid go to school if there's no water there?" (hmm, good point)
It was eventually decided she would just be one thing, a cowgirl like Grandma Kathy. :-)