I'm saying she acquired a weak angreal through secret means very early in her career, and then began using it immediately.

This assumes that use of an angreal means that you are not developing your unaided strength, as you are never pushing your strength boundary, being protected by the angreal buffer at all times.

So in short, as long as Verin never used the angreal to exceed her full natural potential, no one would ever realize that she was channeling through an angreal.

We are told it is a very weak angreal. So lets say she only ever reached 80% of her potential, but the angreal is able to add the missing 20%, thus making it appear that she is channeling at 100% of her unaided potential.

Then no one would ever be the wiser that she possesses an angreal. Which would have been important to her, as angreal are only handed out for limited periods of use under normal conditions.

The entire theory is based on the unproven assumption that constant use of an angreal before reaching your full strength will inhibit your natural strength growth. Which sounds like a dumb bit of logic to me, but which may end up being the truth.