If it had been your idea to give your sister input, then that would be fine. Having your mother basically turn it into a made-to-order blanket turns it into an obligation instead of a spontaneous gift, and that sucks. My feeling on making baby blankets has always been: "I made you a baby blanket. Here you go." They like it, great! They don't like it, they know where the Goodwill is, and somebody there will sure as heck like it. Either way it's not a waste.