Should a female heart patient who experiences hardship from performing Umrah listen to the doctors' advice not to perform it, or does Allah's saying: "Say: 'Nothing will befall us except what Allah has decreed for us'" obligate her to perform it?

Umrah is obligatory once in a lifetime, immediately for whoever is able to find a way to it. So, if one is ill with a non-chronic disease, they should wait for recovery and then promptly perform it. If their illness is chronic and they are unable to go, someone else can perform it on their behalf. However, if Umrah has already been performed, repeating it is a voluntary act and not obligatory. A Muslim should not expose themselves to destruction, for Allah Almighty has commanded caution and granted concessions in matters that are unbearable.