Its so hard, but it is still early days Alpha. Sounds like you are already being a great friend. The practical stuff always helps. No doubt your friend will need time. You will want to do anything you can for her, but the truth is there is not that much you can do except be there for her. It may be you can cook for them if she is eating, and even just be around (some people value the company, others just having some level of normality with others they love close by).
Talking, going over memories, can be helpful. But I can't stress enough that it is early days. Your friend may need you now, but she will definitely need you around for the long term. If you can help her to talk about him/ memories/ how she feels when she is ready, that can be very helpful.
Other practical things can be around funeral arrangements - it just depends on who else she might have around to help her - but no doubt you know her well and will probably know when to step in and when to step back. There are little painful things - finding something to wear to the funeral, speaking with the coroner if applicable, telling other family / friends, cancelling bank stuff. But all these jobs aren't necessarily yours.
My mum died very suddenly at 60, when I was 23. To be honest I valued talking it through with other people, especially those who had gone through a bereavement themselves. And I valued anyone who would just come and be with me, or talk. But everyone is different. Bereavement is a long journey, and we never reach a destination with it, we just learn to walk the journey of life with the loss.