Allah knows what they can see! This could have been hallucination

Once my MOther-in-law told me that when her mother was on death bed in a hospital ,she suddenly started caling someone asking for a mug of water to wash her husband’s feet(her husband passed awaylong ago).and seconds later she was saying that she saw heaven…Sheikh my question is  those who are at the last stage, can they see the people who passed long before.wht is thi