She also said that they understand that XRP shouldn´t be volatile before banks start use it. But what does it mean? And how they achieve it? If they manipulate the price to make it stable, then all XRP investors wouldn´t be pleased.

Crypto nature isn't stable, so I wonder how they want to achieve that, I don't think manipulation will work either. It will be very difficult for banks to adopt XRP as medium of value transfer, once bitcoin falls in price, other alts downfall is imminent.