Ignoring Guards in Rulebook:
If an attacking creature can ignore a guard, it may choose to melee attack a different target in the zone, and it does not have to attack the ignored guard.
Pest in Codex:
A small nuisance creature that cannot hinder enemies. Enemy creatures may ignore a Pest that is guarding to make a melee attack against another target.
Intercept in Codex:
If this creature is guarding, and if a ranged attack targets a non-flying object in the same zone, this creature may redirect that ranged attack to itself, as long as it can be a legal target for that attack.
There is no question about it. A shrinked Angel, that is on guard, may choose to intercept a ranged attack on a target in her zone. Pest and the possibility to ignore guards only concern melee attacks in that zone.