She didn't always take action against the target in question and would instead wait until there was a perfect chance for her to make a move.
And it was precisely because of this that Leo couldn't trust Arya.
If she can calculate an accident, can she calculate this incident and then stayed away on purpose?
However…
The one who ordered Arya to stay in the radioactive zone was Cancer and it was not something that Arya planned. Otherwise, could she have planned for Sarah Kenner to have mission in the Sea Country Base and didn't want the media to look for her.
She could easily give excuse that she let her daughter stay in the place that media people couldn't find.
After all, the opening of this company meant that Sarah will officially expand more in the Sea Country Base in the future. Previously, they only have a few buildings near the edge of the base, which was used for the snipers to borrow the location.
There were too many things that was outside of Arya's knowledge.
