You are absolutely unreasonable to be "effin' furious", yes.
I hope you're not actually effin' furious because if you are it's quite intense, and it's most likely an attitude your friend will have picked up from you. She is going to go through a very very tough time. Her energies are going to be needed for her husband and just making it through the say. She does not need the added stress of trying to keep a friend happy too.
My close friend's husband died very suddenly and unexpectedly. I sent her occasional texts letting her know I was thinking about her with no expectation of receiving a reply or acknowledgement. I never got one. But I wasn't texting her for acknowledgement, I was texting her to let her know in her deepest, darkest hour l, when she was completely alone and not wanting to see or speak to anyone, that people were just waiting. Waiting in the background. Ready to come out whenever we were called on.
I cannot even begin to imagine what she went through in those first few years (yes, it takes years to come to terms with it) and I wouldn't insult anyone who has been through it with trite clichés like "I can't imagine how you're feeling"... They don't care what we're imagining. They're living it. And we really are not important in those moments.
My friend, 8 years later, is now returning to herself. It took her moving away to a, remote location, 4 hours away from family and friends, where she could be alone of she needed to, and she could have people visit, or visit home herself if she needed to.
Grief is not the same for any two people. And it is certainly not about the needs or wants of those around the grieving person.
You can still be a support to her. You can send her the odd text letting her know you are thinking about her. But don't expect replies. And don't be effin' furious that you are not getting the communication from your friend that you think you should.
It really is not about you, good or bad.