The attack happened less than five days ago, this young girl is clearly in shock and had no idea whether or not any of her future concerts may be targets of additional attacks, and given that she was personally in the building during the attack she was involved in that chaotic scene and is probably traumatized by the scene. What do you expect her to say? "**** Islam, ISIS is incompatible with Western culture #westernization" She's a young girl who probably knows just as much about the situation as the rest of us. When she cancelled her tour I'm sure she wasn't thinking "I shouldn't cancel my concerts because then the tefrorists win, even though that not canceling my tour could attact additional terrorists and thus put even more of my fans in danger, but who cares because the terrorists wouldn't win" she was probably thinking "In order to keep myself and my fans safe I probably shouldn't encourage a large number of them to be in one place" which, as we all know, is a terrorists favorite place to go.
All I'm saying is I think we should give her some respect. Thallen I know you're not a fan of the Tumblr/Twitter teenage culture but that's no reason to attack her for the way she responded to the attacks (which is probably how many others would have responded to the attacks). Not only did she experience the attack but it was at her own concert. She's probably scared and confused and is tying to respond in what she believes is the best way possible, and we have to respect her for that. And you can't expect her to suddenly try to use her influence to get her fans to fix the problem. The attack just happened and is raw and we don't even have all of the details yet (and she had even less when she made the tweet) so for her to suddenly start to point fingers on her Twitter account would, in my opinion, be insensitive given how recent the attack is. Maybe she'll speak out more in the future, but for now I think she acted appropriately.
As for her saying sorry, it's just something that people say when something tragic happens. If someone says "my father passed away last month", people usually say "I'm so sorry" not because they did it but because it's just something that you say when something like that happens.