Try to use this command "property.extensions[0].value".
I also need it to use in my UI5 APP where I have to create a dynamic Table. I can read Entity Fields by using "property.name" but to read labels for the relevant properties I got a solution. That is "property.extensions[0].value"
var oMeta = oModel.getServiceMetadata();
var oControl;
for ( var i = 0; i < oMeta.dataServices.schema[0].entityType[0].property.length; i++) {
var property = oMeta.dataServices.schema[0].entityType[0].property[i];
console.log(property); // To read the property attributes
Regards
Khabir Ahmad Raja