Best Friend... or Ex-Friend ? What is she?

I have been best friends with 'Cathy' for 15 yrs. this past winter her daughter died. Ever since then, she will not talk to me. Everything was hunky dory during the weeks prior to her death and through the fumeral process. Then, suddenly, she will not take answer my phone calls, will not return calls after I left messages on both the machine and with teenage grandchildren. I sent a check for several hundred dollars to her for the memorial fund and I did not even get a call or a note of thanks. She would not come to the door when I would knock.
I did speak with her husband once during these past months, and all he could say was that she is depressed. Another phone call led to her stepdaughter answering the phone and when I asked to talk with 'Cathy' she said ...."Uh....Uh... she ...uh ....she is laying down.". I can just see my friend whispering or motioning for her to tell me she does not want to talk. ( I have witnessed this behavior when I was there and someone would call that she didn't want to talk to.)
Another one of her friends told me that 'Cathy' did the same thing to her. And then 4 months later, just called out of the blue and acted like nothing ever happened.
Queston - do I continue to attempt to contact her? Or should I just write her off as my friend.?