In first "version" of her intentions,
when surgically altered Troi orders her to alter ship's course to the Kaleb sector
she replies, that this would mean entering Federation space, which can be taken (by other side) as an act of war. And, contrary to what most of Tal Shiar members thinks or ants, most of the Romulan ship's commanders wishes to avoid war with Federation as much as possible.
when it turns out, that USS Enterprise is able to detect presence of cloaked warbird
she decides, that she will attack and destroy the Federation ship. This would, of course, mean an act of open and unjudged aggression and therefore -- an act of war. She wanted to avoid that some time ago, so this means a 180 degrees change of mind or point of view IMHO. Not mentioning, that with this decission, she is ruining the chance to examine a technology (new to Romulans) of detecting a cloaked ship.
when Toreth realizes, that Major Rakal / Troi is not who she appears to be and that most likely she and her ship is in the middle of betrayal of some high Romulan officers and that a strange, maybe dangerous to Romulan Empire cargo was transported to the Federation ship,
she decides to set a course to Romulus, instead of attacking the Federation ship. And she is changing her decision and point of view again.
My conclusions / misunderstanding:
(1) She is trying to avoid a Romulan-Federation war, by all her means. (2) She want to destroy a Federation ship only because she has some doubts, that it can detect a Romulan cloaked ship, risking a new war. (3) She finds out, that a strange cargo was transported, that there maybe some spy work or betrayal on her ship, but in this situation she resign from destroying Enterprise and decides to fly to Romulus.
This just doesn't make any sense to me.