Is a woman performing Umrah whose husband died in Mecca, and who intends to stay for Hajj (voluntary Hajj), obligated to go out for Hajj? And where does she observe her 'iddah when she is not in her home country?

It is permissible for a woman to go out for Hajj if she has reached Makkah and her husband passed away, due to her distance from her homeland. She should complete the remainder of her 'iddah in Makkah after the rituals if she is able to stay and is safe from fitnah (temptation/strife). Otherwise, she should return to her homeland and complete her 'iddah there.