It sounds to me like this girl is either in the thick of it ans confused and maybe wants confirmation of an abusive relationship between you and him. She could also be trying to build a case against him or maybe he’s fed her false news about you…
She’s maybe been put off speaking on the phone by the fact you said you would have your partner listen on loud speaker because it’s a hard topic for her to talk about. Maybe she’s paranoid or afraid and doesn’t trust that you would not inform your ex..