When my DH died I would tell everyone I was coping "just fine thanks". It was easier than watching their horror as I slid to the floor and howled like a wounded animal.
Many of my "friends" drifted away in terms of their support 3 months or so after DH died. I think it scared them that I would need them for an indefinite period. I was a burden to their happy perfect lives.
The best thing you can do is be there and be there and be there and be there and be there and be there.
There is no time limit on grief. God knows, it's 11 years next month since DH1 died, I cried like a baby last night with DH2 when we talked about some of my memories.
The best gift you can give her is to let her talk.
People would try to jolly me along, change the subject, lighten the mood.
When the one person you planned to spend the next 50 years with has been wiped off the face of the earth it takes weeks, months and years for you to come to terms with that concept and the best way of achieving that is by talking.
Just be a quiet ear. Hear what she says and don't feel as though you have to offer solutions or platitudes.
It won't be easy for you, bless you for caring so much.x