After 6 years since radiation, I am again a sun worshipper although now in sunny Arizona.... so I do watch my sun worshpping...I can't tolerate too much but it will slowly get back to normal for your mom. It was rough in the beginning since my area is still quite numb (damaged nerves I guess during operation) with very little feeling coming back...cannot feel extreme cold...but the sun should be done in moderation at any time. At first, the sun bothered me and now I love it again. It takes time so tell your Mom to relax and enjoy it little by little...