There are too many coincidences at work.
A few i admit.
There's no way she could have predicted Dorothea rescuing her
Probably not no, but even so, Dorothea admits Leliana could have escaped WITHOUT her help, in the very DLC she helps her escape.
There's no way she could have predicted the Blight happening.
No, But then she didn't pick Lothering herself, although that turned out to be very, very beneficial.
There's no way she could have predicted the Warden coming through Lothering.
Incorrect, It's the first major settlement outside of the wilds for hundreds of miles.
Given the battle was going to take place at Ostagar, she likely saw the royal army going through lothering on their way down the Hinterlands, along with the greywarden vanguard.
Inversely, it makes sense for her to assume they will return the same way, this is further confirmed by A, the army returning that way, and B, every one else for a hundred miles going that way.
And frankly, banking on just two Wardens successfully beating the Blight when they have been branded criminals is monumentally stupid.
Is it? The Grey Wardens of the first blight faced worse odds, and yet they sill won, beyond that given that all life will perish if a blight is not stopped, there are many reasons to make sure the grey wardens DO succeed. Beyond that? It gives her a way out of Lothering and thus the advancing horde, and to get away from those spying on her.
It's the longest of long shots.
It's a gamble, but all of her life was a gamble, and this one had better odds then most in my eye.