Hi there, it's perfectly natural. My mum struggles to sleep also, it's more the getting to sleep and staying asleep. It's nearly 8 months since my dad passed. Is your mum worried about not sleeping? If so I'm sure the doctor would prescribe something if suitable. I'm sure your mum has lots going around in her head at this time. I had lots of trouble sleeping for several months for a whole host of different reasons. 

Im sorry for your loss at this sad time also x

Just to say my mam passed away 3 weeks ago & dad is struggling to sleep. He says things are going round & round in his head but last night he had no sleep at all. I'm worried about him as he is fighting his own battle with cancer & is 80! It's reassuring to know that this is a normal part of the grieving process though. Xx