There are any number of possible explanations for this, including that she is simply taking a break.  It's not clear how much effort you have put into trying to reach her but at a certain point, providers may get nervous if someone is overzealous in trying to reach them.  Move on to someone else and perhaps try her again later if it looks like she is active again.

I used to see her about once a month and she has not responded to my messages lately. Perhaps she has retired, who knows? She has done this before in the past. Does not matter, I found a new ATF in Casey anyway.