Not much to add to what others have said. Learning treble clef is always a good idea if you ask me (and bass as well, at least passably, even if one always plays treble-clef instruments and doesn't sing in the bass clef-- I can read bass clef well enough to get by, but I'm not as fluent in it as I probably would be had I taken the time as a kid). Once she's used to both, she'll be able to switch back and forth easily (I always have to practice at alto clef a bit but that's because I only pick up viola once in a blue moon and don't keep it in my mind-- after about ten minutes I'm reacquainted enough for it to be easy).
And, even if she starts on violin, she may be like my mom and eventually switch to viola anyway. Plenty of violin players tend to pick up viola in addition as well (like me and a lot of violinists I know) and play both. It's one of those things that seems almost like a no-brainer-- the skills are transferable with little adjustment (unlike, say, switching from violin to cello or bass), so why on earth not do it.
Thanks for the input. Her first viola class was canceled and I didn't go to the next one so I haven't been able to ask her teacher about all this.. maybe this week.
I'm curious, if one plays violin and wants to play viola.. I know they have 3 strings in common, but it seems that changes all the fingering patterns by shifting them up/down one string. Is this easy to do? Like a guitarist using a capo? I'm curious how that works.
Her viola is a very small one, too small for her actually but that's what they gave us since it's only for 6 weeks.. so for her I don't think she really sees any difference between violin & viola. I explained to her that the strings are shifted higher by one string and the violin plays a little higher. So I think it's really not going to be a problem for her to choose violin even though her 6 week introduction is on viola. And there are more violin teachers so more flexibility in scheduling lessons (compared to one viola teacher).