I am very sorry for your loss.
I was very grateful when a school friend of mine persistently called to me every week for about 2-3 months after my dad died. ometimes we didn't talk about him at all, just chit chatted, but the company was nice.
When my father died, or at least afterwards, I helped my mother clear out the medical press and dispose of the left over pills, helped go through all the cards, read them together, weeped, thought about the mortuary cards.
My advice would be just be there for her, help her when she wants to do something, but don't push anything. Let her take the steps that need to be taken in her own time.
My friend who called to me (who lost her mum in her 20's), told me it takes 3 years to get over a death like that. Well I am just over 1 year into the process and from my experience, the first year is very hard. It is not a fast process. Sometimes people will laugh and joke and have fun, and you will think they are ok, but grieving takes time. Losing a parent is something I think you never really get over, it changes you, but you do appreciate the people that support you along the way.