I'm just over two years in, and am down to about six friends out of a wide circle who appear to give a shit. My circumstances are a bit different. I'm a bit older and my kids are grown, however, I would say bear in mind this is a long haul situation.
What I've found - though I appreciate every situation is different - is that people can come in hot and heavy for the first few months, then "normal" life resumes for them, and one can feel sort of bereaved all over again. So it sort of requires a bit of commitment I feel.
Of course as a widow you have to adjust, but it changes you - it turns your life upside down, and I've come across barely disguised frustration that I haven't picked myself up and dusted my self down fast or stoically enough.
You sound lovely and I appreciate that at a distance your ability to help practically is limited but from a personal perspective consistency is key. I appreciate that it's a fine line to tread - supporting someone through such a devastating loss is hard. Regular check ins are ideal, and also remembering that with such a loss can also come a loss of sense of self, never mind the loss of their person.
There can be an element of "putting a brave face on" because that's what's expected, while someone is really deeply struggling and might need to express that.
Isolation happens by accident - a tribe may assume that everyone is doing a bit, but maybe nobody is.... and it can feel rude to ask because everyone's got stuff going on. I have felt a bit like a baton in a relay race, and my trust has been eroded in both the wider world and myself and people around me too.
I'm sorry if I'm being a bit heavy and gloomy, but in a nutshell I think when you send cards and messages, try and make her feel valued for herself as much as for her situation if you know what I mean? It's hard to explain. Just before Christmas I had a complete meltdown because I felt as though I was "just" DPs widow, if that makes any sense.
Sorry, I'm waffling on but I wanted to try and give you some pointers. As I say, everyone's experience is different on both sides. Just keep the lines of communication open as much as you can xxxx