If I wanna be really generous to Sotomayor she might only be talking about in her capacity as a Supreme Court Justice. Since the only changes that can be made to the Constitution have to be ratified through either the house+senate or a national convention called by the states. For anyone in the judicial branch, the constitution might as well never change because it's not their job to change it or propose changes. Their job is to interpret the words and say what the constitution means.

But yeah if just a normal person says the constitution can't change that's nonsense. My favorite is when some chud will say the constitution is final/immutable and yet they'll have a 2nd amendment tattoo or something. Like dude the 2nd amendment is a change that was made to the constitution.