I don't think it is too early at all. And I agree with other people that I personally see music as a core skill that helps so many areas of their lives. Including and especially dance. It emphasises their ability to find the pulse in a piece, listen to the heart of music. Good dancers are often good musicians because they can feel the pieces inside them and have the coordination for hands doing different things and such.
My daughter started piano in FY and clarinet in y1. At the time she was doing dance and swimming still. She finished swimming in y2 when she'd done all the pre-competitive grades and I have to admit it was good to lose that expense. Her music lessons are private rather than school lessons and are one of the biggest expenses in our life. But they're one I have made many other budget sacrifices to carry on paying for.
My daughter understood waltz time long before she came across it in ballet, she knew about adagios and allegros, about finding the time signature etc. Music taught her fractions. Because she started fairly young, practice is now something that is simply part of the routine.
As others have said, you need to be on board with it as something you're committing to as well because your support during her practice will make a big difference. When she first starts, 10 minutes a day will be fine. My little one absolutely loves her music and it is now a huge part of our lives. She practises for a significant chunk of the day and does bands, workshops, goes to all sorts of concerts. But the size of the commitment it is depends on what you both want. Though the size of both of your commitment also will determine the progress.
Specifically with violin, the others are spot on that early progress can be slower than some instruments but it's so worth getting a good fundamental technique and doing it properly. It's a very beautiful instrument.
In terms of your ability, i wasn't very musical when she started, but I learnt as she did and ended up taking piano lessons myself & it was such a good decision. I started for her and carried on for me. Because of her love of music, weve had experiences I would never have dreamed of and she's got opportunities ahead of her that are so exciting.
In case you haven't gathered..... I would hugely encourage you to go for it xxx