This comes as no surprise to me. Nor do I see it as an indication of guilt or innocence. In all honesty, if I were falsely accused of a crime and had told LE all that I knew, yet suspected that they were still eavesdropping on my private conversations, I'd be buying bat phones, too.
On the other hand, it does tell us that if she and/or her friend(s) were savvy enough to buy a bat phone after the crime, she could've owned one prior to. But that's not much of a surprise, either. My big question is which friend? The article implies, albeit subtly, that DeDe purchased the phones. (The way I read it.) Whether it's DeDe or not, I wonder if the friend bought one for herself, as well.