Is a daughter considered undutiful if she asks her mother to postpone Umrah, using saved money, out of a desire to await news of a scholarship, especially with her fear of not having enough money for either the scholarship or Umrah later?

There is no doubt that enabling your mother to perform Umrah by paying its expenses is considered one of the greatest acts of obedience and most excellent ways of drawing near to Allah, due to the righteousness and assistance in obedience it entails. However, it is not an initial obligation, because it is not part of the obligatory maintenance a child owes to their parent. Nevertheless, enabling her to perform Umrah may become obligatory if she requests it and the child is capable. So, if your mother asks you to enable her to perform Umrah, obeying her is obligatory, and her obedience takes precedence over studying abroad.