I bought a pair of the ‘hard’ ones to use with 140mm shocks. The bars are rigid. More so than the narrower Answers they replaced. I’d be tempted to try the ‘chewy’ ones as I suspect they’ll have a gentle amount of ‘give’ that might reduce buzz.
Rather than twiddle with bar brands, try playing with her position. I got a ‘cross bike the other year and even on short rides I’d end up with tingling and numbness in my fingers. I dropped the stem, shifted the saddle, changed the lever and bar positions and it’s all OK now. Took a few days of trial and error to get it right.