Friends of the Marriage, Friends of the Affair

Once an affair is blown open, it's almost impossible not to draw a line, divvying up friends who are collateral damage of the affair...and those who can be brought forward into the new reality.
Friends who knew of the affair but did nothing to discourage it can seem threatening, justifiably so, to the partner who feels betrayed not only by his/her spouse, but by a friend who seemed to offer implicit approval. Friends who did, in fact, assist in the deception, by offering alibis are clearly not "friends of the marriage". And I've heard plenty of tales of "friends" who seem to gain some sort of vicarious thrill by actually encouraging the affair.
While my own experience has none of the drama of that, I had to cool things with one my closest friends, whose own marriage was destroyed by her husband's affair, because she didn't seem able to handle my own emotional upset. Conversations in which I brought up various issues (cutting the Other Woman from our life, for example) were cut short with a "well, I couldn't stay with him" and seeking advice only got me more of the same. There was one way to handle an affair in her estimation: Dump the loser and move forward.
Other friendships haven't weathered my new reality either. Some friends seem unable to let go of it themselves, bringing the topic up though it doesn't seem warranted.
Though I've never experienced serious disease or the death of a child (and pray to God I never do!), I suspect it raises similar issues: There are those who can be there for you in ways that propel you forward...and those who, for whatever reason, simply can't.
Nonetheless, it can seem like simply another loss during a time marked by losses. Of your dreams. Your convictions. Your family.
Unfortunately, many people simply can't cope with BIG pain. Or can't cope with you dealing with it in a way that isn't consistent with how they think you should deal with it.
Your challenge is, of course, to take care of yourself. Surround yourself only with those who can offer strength and support, whether you've chosen to confide in them or not. Good friends will leave you feeling buoyed...which will help you cope.
That said, sometimes friends offer us advice that we don't want or aren't ready to hear. Ensure that you're not shooting the messenger, even if you're shooting down the message.