How did Delenn sense the Keeper on Londo and why didn't she do anything about it?

Question

In (I believe) Objects At Rest, Delenn sensed the Keeper on Londo. How could she sense it and why didn't she do anything about it?

Answer 1

It was implied in season 1 that Delenn had an implant that could detect the Shadows.

Delenn meets Morden

We can assume it may be reacting to Londo's keeper as well. But it is an assumption.

Edit: Additional comment - She can't do anything because she doesn't know anything. Even if she had complete knowlege of Sheridan's trip to the Future of Centauri Prime - Sheridan was certainly operating on the mistaken assumption that if he went to Z'ha'dum he was preventing that future. So She is not connecting the dots like the audience can.