Sirius, I need you to set off at once. You are to alert Remus Lupin, Arabella Figg, Mundungus Fletcher... the old crowd. - Albus Dumbledore
The above quote (from Harry Potter and the Goblet of Fire) refers to members of the original Order of the Phoenix, from the wizarding war against Voldemort.
The name which particularly interests me is Arabella Figg, also known as the Dursleys' elderly neighbour with a house that smells like cats.
It's later revealed that:
She's actually a Squib (wizard-born, but no magic) instead of a Muggle
Helps Harry and Dudley escape from the dementors.
I fully realise why this would offend Voldemort and the Death Eaters, and why Mrs Figg would be at risk during the first war. I just don't know how she'd be able to participate in active resistance against a merciless magic-wielding army.
Wouldn't she actually be a liability to this group? She'd have no means of defending herself if she were to be tortured, or subject to legilimency, to reveal the whereabouts of the rest of the Order.
Why was Mrs Figg allowed to be in the Order of the Phoenix? What was her role in resisting the rise of Voldemort? Are there any sources for this?