I can totally understand her thanking her mom, because "piano helped her in learning shamisen". It's always like this. If you learn an instrument, or some music theory, or at least do some level of careful music listening; learning a suitable instrument becomes surprisingly easier. I write from experience. It can especially help for self educated learners.
I will not talk about my whole experience. But trombone quiting violin after 1 year feels very easy (I play euphonium now, but I started tenor brass instruments with trombone, and I still play it sometimes for fun. They share the mouthpiece and play similarly). There are so many analogies. Instead of playing multiple strings, we play multiple harmonics. Both instruments have no clear note positions, so you can use violin etudes to play notes correctly. Violin is more versatile, though. But then, trombone has a breath exercise that can be a bit relaxing. And in general, I learned tons of things from my teachers during my short violin adventure. It's helping me so much.
I also very occasionally play violin, because it's nostalgic, and I feel sad about having to quit it (it's just too difficult, and caused problems with other things at the time).