Is it normal to cry every night three years after losing a partner?

I’m worried about my grandmother. We lost my grandpa three years ago. My grandparents had been married for 50 years. So it was undoubtedly tough for my grandmother as it would be for anybody. I was just doing something in the hall outside her room before going to bed and I heard her kind of singing. And then I heard her speaking and crying saying ‘wait for me’ and telling him she loves him. I understand she will forever be grieving, but I do worry about her going to bed at night and crying. Is this worrying behaviour or just her normal way of grieving? She is totally fine during the day and clearly bottles up her emotions for the evening. Is this unhealthy grieving?
Is it normal to cry every night three years after losing a partner?
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