While I would agree that Weaver Widow can be situtational, I have found that "situational" is almost every situation. She comes with multiple strengths which all directly buff Collodi's crew.
First, she is arachnid which lets her ignore annoying terrain penalties. She can even scout into buildings and chase down snipers if needed. Then she picks up a corpse counter after the kill.
Second, she is both a scavenger and graverobber. While the graverobber doesn't help Collodi, it allows you to let Collodi pick up his broken marionettes and the Weaver to deny Ressers of their dead counters. You will put them to good use with point three.
Third, she acts as LoL's Annie. In fact, that is the name of my Weaver. Teddy (or Tibbers) is a huge target on the field. Doing a Tibber drop after getting 4 counters is a gratifying experience. This will occur at turn 4 at the latest and most-likely earlier as deaths occur.