Darren,
There are several solutions to the issue of playing live and solo. I can't tell of personal experience, because I don't. However, depending on what you want to do would determine how you do it.

1. Do you want to play a fixed length song, or be able to vary it. Since you daughter is 12, I'm going to assume that she wants to play a fixed, known length song every time. The variation comes from the Conductor feature of Band In A Box, which is very sophisticated, but comes with several drawbacks, including not being able to use Real Tracks.

2. What sound quality do you want? Using Real Tracks feature of Band In A Box means awesome quality sound being generated each time, but can take a couple of minutes to load each song, something no performer wants. The song has to be ready to go NOW, with no dead time. Real Tracks can be saved in a song using a Digital Audio Workstation like Real Band or Sonar, and then saved as a wave file or mp3. However, it'll always be the same, none of the spontaneity that BIAB will give you with each song play.\

3. You can use a MIDI synth, but the higher quality device requires you to spend more money. The most 'bang for the buck' right now appears to be the Ketron SD2, which you can purchase right here on PG Music's webside for $379.

4. One of the things I'm not sure of is if Kayla plays guitar. If she doesn't, do you have a guitar player? She does have a lovely voice, by the way. Most of the people who play out have at least one instrument that they play. Band In A Box is not going to give you the finished track that you could get from a professionally created backing track, at least right out of the box. For most musicians, not all, BIAB starts as a place to start from, and then tweak to a final product. Some of our jazz musicians may just use two or three of the parts, and play in a trio or quartet style, but it sounds as though Kayla needs a full backing track, and that will need some work.
I'm not saying it can't be done, it can, but it will take time to get everything right for her.

I wish you luck in your endeavors with her, she is a talented young lady.

Gary

I'm blessed watching God do what He does best. I've had a few rough years, and I'm still not back to where I want to be, but I'm on the way and things are looking far better now than what they were!