Posner covers her in his book Case Closed. The way he paints her in that book does not make her sound credible at all.
Yes, I've read the interviews of her; by the late seventies she was, frankly, a racist nut. Or a nutty racist. Either way will do although I believe she was a pro-segregationist/racist in the sixties as well.
Although if Oswald did meet with Banister, as she later claimed, then why not mention it to Garrison's people? And wouldn't Banister have mentioned that to her? After the assassination? I've read other accounts by people who say Banister would get information from leftist and rightwing groups - an assortment of characters; it was part of his job. Finally, Gaudet phoned the FBI in New Orleans five days after the assassination and never mentioned seeing Oswald before - with Banister or otherwise.
Anyway, in that interview with Garrison's people she comes across as credible. Or at least not unbalanced.