Musical instrument

Viola will get her more opportunities earlier in terms of ensemble playing whether that be orchestras or chamber music. But yes you can easily enough change from violin to viola or add it in (both my university age children play viola a little off the back of being violinists, mostly on borrowed instruments). If she started on viola but got really good quickly I'm sure she could easily add in violin too.

It is not uncommon for children to be drawn to the sound of one instrument ahead of the others, so do ask her what she thinks and pay attention to the answers.

Cellists definitely end up with the responsibility for transportation. My violinist sister has two cellist daughters and they used to refer to "cello tetris" getting two instruments in the front passenger seat, that stopped once both needed 3/4 sizes or possibly earlier. When my sister was university age, it was always the cellist who drove to quartet gigs.

Yes double basses are a big transportation issue - but in many contexts instruments may be loaned to reduce the need to move them around.

Finally, violin (let alone the others!) does not have to sound bad even at the beginning - take the time to listen and enjoy the sound you produce, work on open strings loads, and you can get very tolerable results quite quickly. (massive COI - I'm a Suzuki violin teacher)

It sounds a great opportunity, I hope you both enjoy it! Good luck.

I know someone who used to get a double bass and several children in an (old size) Mini - never was quite sure how she managed that!

I still like cello more, though

I learned the full size double bass. It fit into a Citroen Saxo when my mum was carting me around the county as a teenager!

One advantage of a lower pitched instrument is it's less squeaky when a learner is playing it....

The reason for putting mini bass above viola is firstly that it uses a more generally useful clef (bass clef rather than alto clef) but also it could lead on to bass guitar as well as a full (or 3/4) sized bass, whereas wit( viola you’re pretty stuck.

I’m biased but cello would be my first choice.

She’ll start on an appropriately-sized one and they aren’t THAT much of a pain to carry around. They are also way less painful on the ears than beginner violins!

Then violin, mini bass and viola in that order.

Don't let her learn bass unless you are prepared to move a fully sized one around later.

Most viola players started on violin they are very similar. The violin is probably easier to start on and and the music is easier to read

Never played cello so won't comment.