can Widow Tarha use her Hero Ability to reroll an attack or power die when her reanimate familiar figure attacks?

I dont think so. You is the hero in question not the familiar.

I dont think so. You is the hero in question not the familiar.

The player who controls the familiar figure also controls Widow Tarha, so he/she should be able to use the ability on his/her turn no matter which figure is attacking.

Incorrect, the ability refers only to Widow Tarha's attacks. It does not apply to the reanimate.

To reinforce Whitewing's reply, that exact question is listed in the official FAQ.

Q: Can Widow Tarha use her hero ability on attacks made with her Reanimate?

A: No, Widow Tarha’s hero ability only affects her own attack rolls.

Each figure's skills, abilites and feats affect only them, if it says you. If it targets another figure, the wording would reflect this.

This is why so many familliar's get their "attacks" through their summoner, like the conjurer's Mirror Image or the geomancer's stones. The summoner attacks through the familliar, using his own weapon. If the familiar's attack does not use the summoner's weapon, it's a safe bet it's because his attack is not made by his summoner.