TGH chapter 7 PG. 102.

'How will this affect matters?' Moiraine wondered. 'He is not necessary with the horn gone, and yet...'

 

In reference to Mat being ill from the dagger being stolen

Moiraine is awesome.

Moiraine planned to use Mat's sense of adventure to lure Rand into taking the Horn south. With the horn stolen, that plan was useless, and so was Mat--until she constructed a new plan.

 

Both plans failed, incidently. Moiraine did her best, but she was far from being all knowing.

Moiraine planned to use Mat's sense of adventure to lure Rand into taking the Horn south. With the horn stolen, that plan was useless, and so was Mat--until she constructed a new plan.

 

Both plans failed, incidently. Moiraine did her best, but she was far from being all knowing.

She just seemed a bit too fast to discard Mat at that point. At least in my opinion.