ANSWER:

Her iddah is like that of any widow, whether old or young: 4 lunar months and 10 days. 

Sheikh my grandmother is 70 years old and my grandfather has passed away. What is the ruling for the LENGTH of her iddah? 3 months or 4 months 10 days. Would like to see some evidences too.

Waiting Period of widow or divorcee | November 28, 2018 3:09 am
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I wanted to know clearly. When does it become mandatory to redo the marriage for husband and wife. My husband gave me talaq 2 times. Both in different occasions. After 2nd one we got together then he left to other country and we were not talking for 2 months, cuz we were still upset with each other. Some say we have to renew or nikah.
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Permissible reasons for a Widow in her Iddah to go out of the house – Sheikh Assim Al Hakeem