Maybe. Shio was abducted and kept imprisoned in an apartment. Satou was sending information to her relatives to let them know she was alive. That's just the right thing to do.
Shouko doesn't know that Shio has been abducted nor does she know she's imprisoned. And no, it's not the right thing to do to blindly interfere in a situation that she knows full well she doesn't properly understand.
See? That picture was probably the only reason she lived as long as she did. As evidenced by Satou's line right before she kills Shouko, she had already decided she would never trust Shouko again long before she ever took that picture.
Well you say that, but if Shouko hadn't taken the picture and had been a lot calmer, more sympathetic, less judgemental and y'know, generally more trustworthy, I don't think it would have happened. Satou wanted to be able to trust her.