To me it seems easier to play music in your free time than art. But I'm more musician than artist as it is.
With art you need supplies, a specialized place to work on it, and depending on what kind of art you pursue, you need knowledge of the materials (though at her age it's probably just painting, drawing, and ceramics) and she probably doesn't have regular access to those things (unless your parents are artists?)
And it would probably be more expensive and less productive than music if she doesn't know what she's doing.
And if she plans on getting into art school she needs as much time as possible getting familiar with a wide range of mediums and a portfolio. I discovered art very late so my pieces are few and not varied enough to make a satisfactory portfolio and I completely missed drawing and apparently that's pretty big in the art world
.
With music you can just roll out of bed and have at it, sure lessons and technique are a part of it but not like art. Outside lessons are also much more accessible in music than art. Unless she runs through keyboards or vocal cords really fast
To get into music school all you need is a stellar audition.
To me, your sister sounds more then good enough to practice music on her own. But then again I haven't seen her art or heard her on the other instruments and I'm easily impressed by young singers because I'm not a true singer myself.
And on a side note.....music and art not at the same time? If I may quote SNL's Keenan Thompson "what's up wit dat?"
