Leah: As others have stated, there really isn't such things as 'Girlie Keys.' My wife and I play all kinds of songs together, and our voices are comfortable in the same key. She an octave higher than me. Depending on the melody, we sing stuff in many different keys. I think what you need to do is learn how to transpose. The Coo-Coo Bird is in G mountain minor, as played by Clarence Ashley, and my advice would be to learn it in that key and then figure out whether that tuning is too high, or too low. You've probably already done this. Then, what you need to do is either capo up to your range, or else tune down to it. In extreme cases, you might want to transpose the tune into another key, hence another tuning. I've done this with several songs. Sure, the song is gonna have a different 'color' to it, but that might not be a bad thing.

If you do find that you have to tune down to get to the place where you feel comfortable, you might want to try experimenting with heavier strings so your banjo won't sound so 'floppy' and dead. I do this on one of my banjos that I keep tuned to 'E'.