@Giblow20 There would be time to react because they're using a flare to signal to the attackers. She actually has more time to act than the attackers because she is looking directly at Armin and can see his movements and the flare on his hand before the attackers can see/hear the signal. They also have no reason to think she wouldn't notice people sneaking up on her since she is a trained soldier. And she does notice and does react (chapter 32, page 3), if one of the attackers had a blade, she could've simply thrown herself at the blade instead of trying to run.
>restraint isnt the safer option because u literally see it failing next chapter
All plans have a chance to fail, a plan failing has no bearing on the risk mitigation associated with it because the amount of knowledge you have before and after execution is not the same. Take the ring as an example, they have no way of knowing she has that ring before executing the plan, therefore it cannot be taken into account when planning.