<p>As others mention, the health concerns are paramount.</p>
<p>I'm no expert, but I'll add my 2 cents from experience.</p>
<p>The instrument is indeed larger than a violin, but non standard in size. You will have a wide range of options in finding a playable yet decent sounding instrument. A true viola bow is also a bit heavier. And of course, you're playing in a different cleft. Fingerings, bowings, hand positions, technique are similar, but not identical to the violin. The nuances can be the stumbling blocks, and can result in discomfort and pain.</p>
<p>If it's painful, STOP.</p>
<p>A trained violist is better suited to guiding you through proper instrument sizing and tonality, playability and instruction than a "pure" violinist.</p>
<p>Is she at an advanced level on the violin? I would not recommend doubling for an intermediate player, other than occasionally "fooling around" for fun. </p>
<p>However, if she thinks she may want to pursue viola seriously, engage the best viola instructor you can, not a violinist who also teaches viola. If she wants to do both, the instructor should be trained in both, and actively be playing both. You may have conflicts with two instructors, one on violin, one on viola. They will be at loggerheads. A solution is to have a pedagog trained and versed and playing both instruments at a professional level. Getting to "that next level" can be extremely difficult for some while actively playing and learning both simultaneously.</p>
<p>Advanced proficiency on both requires time, dedication, and an ability to separate instruments mentally. That's how violason describes it. I know it sounds a bit weird, but that's how he described switching when learning violin. He also said it seems that most have less difficulty going from violin to viola than vice-versa. Son was a violist from the get go, but he also had high level training on the violin, but only after he had reached conservatory level on the viola. He has played both professionally, but knows his limits on the violin. </p>
<p>A trained violist is better suited to guiding you through proper instrument sizing and tonality, playability than a violinist who dabbles with viola. </p>
<p>I've seen good violinists become excellent violists, but I've also seen good violinists become less than mediocre violists, due primarily to bad instruction.</p>