This seems overly harsh. I'd compare it more to someone taking time off to deal with a personal tragedy. She deserves to take some time off and when she's ready her fans will be excited to see her.
I'm not saying she doesn't "Deserve" it, it's her tour and her life, she can do whatever she wants. It would be insane for anyone to say otherwise.
And I fully understand her reasoning. I've been in similar scenarios and I was scared/nervous too.
I just think it's a bad thing for the world from a pragmatic perspective. It's rolling over and submitting to terrorists. Which is bad news for everyone.
Open a question to the floor, why do you think all civilization promote a policy that they do not negotiate with terrorists?
Because the moment you do negotiate, you communicate to them and all other terrorists that terrorism works and is a viable means to an end to achieve a goal.
This is an extension of that. Terrorists look at this, go "Look lads our shit works, they're terrified and giving up." and so do more of it.
Is it confirmed that she's cancelling all her tours or just like a suspension?
I don't know if I'd consider taking time off from her tours as giving in to terrorism. If she negatively changed her character and came out of this with "worse" views due to the attack then you might have a point. ---