Basically everything Tickly said, and just keep in front of you that grief is not linear.
I have a close friend who lost her DD in tragic circumstances, so all the paperwork exacerbated the situation, I have this close friend because strangely enough I didn't know her before her child died, I went up to her at the funeral and said I am FF, your child was unspeakably kind and inclusive to my child when he had no friends, I will come and see you in six weeks.
Even in the depths of her grief she looked at me and said that is very specific, I replied everyone will have gone back to real life, I will see you then.
I went around and knocked on the door, gave her a hug, let her cry and that was that, we have been really good friends ever since.
I don't crowd her, but I am always there (by text) also when I am buying flowers for myself I will buy a bunch for her and leave them on the doorstep, that way if she can't face the world she doesn't have to.
We have a shorthand now, and if she is sorry she missed me, she texts to say thank you for the talking flowers and I will call and we will chat, well actually I just let her talk. Other times it is thank you for the silent flowers and I will wait for a call.
Just be there in the background it is all you can do.