I recently lost one of my parents. They were close to one another, neither of them really did anything alone or had their own identity/hobbies/interests outside of their marriage.
Called round to visit earlier and mum casually dropped into conversation that she hasn't seen anyone since Wednesday 
One of my siblings does 12hr shifts, four on and four off. She had been round Wednesday and they'd gone out to lunch. I haven't been round before today as my DC have had a sick bug but I have been phoning and texting daily, usually I call round 2-4 times a week depending on my work schedule. Other sibling has moved in with soon-to-be BIL at Christmas and is very much in that loved-up 'bubble' but is a freelancer and currently on a period of downtime, she has not been round in over a week. We all have good relationships with each other, there are no feuds or tensions. I know they've been phoning, same as me, but I'm sad my mum hasn't seen a physical person in days.
She won't join any clubs, I think she'd enjoy it if she did but she has confidence issues and doesn't like striking up conversations with people she doesn't know. She doesn't have many friends. She has contacted friends she has and they did really round a bit in the immediate aftermath but now they've all drifted back to their own lives and she doesn't want to 'bother them'. She still works but isn't social with the people she works with outside of the work environment.
She just seems so diminished and I'm really worried about her. I think she's a bit depressed, not surprisingly, and probably also traumatised as my dad's death was not peaceful, expected, or clean and she witnessed the entire thing. She won't entertain talking to anyone about it as that's 'wallowing' and we don't wallow.
What can I do to help her? She's only 60 so has plenty of life ahead of her, I hate the idea of her spending it being lonely but I don't know how to support her through this bit while also grieving myself, working, parenting, and all the other stuff.