Maybe Mary Cain is just trying to surround herself with good vibes and positive things after dealing with a tough year physically, emotionally and training wise. She probably had to deal with some backlash (whether on Letsrun or otherwise) when she wasn't able to make the results happen this year, in addition to all the craziness surrounding NOP.
As Letsrun is notoriously a hub for the not-quites, has-beens and hobby joggers of the internet to come out and criticize professional runners when they are having an off day/year, I can understand wanting to stay away for awhile while trying to rebuild (especially at age 19).
I'm not saying I'm not a fan of Letsrun, I totally am, but I understand where she is coming from. As a more seasoned professional, I'm sure it would be easier to simply avoid the chatter on the internet or handle an interview during a rough time with grace. However, she is young and I really get the sense that Mary Cain has made a real effort the past year to not let these things bother her. (Avoiding this interview, staying out of the limelight, comments about staying off social media, not posting, etc).
I get that she did another interview, but as mentioned, there weren't the difficult/prying questions. Also, depending on whether or not she reads or has read Letsrun, the association may just turn her off. In the interview she gave, she could just be bubbly happy Mary Cain and move on with her day.
I'm not saying I agree or disagree with her choice not to talk to Letsrun, but I can see where she is coming from. As long as its working for her and she is getting better again, I'm in support.