My father passed away January 2018, in Sept 2017 she got POA over my father and had him put her name on his bank account. Is there anything we can do?

We know this was his life savings at 90 years old. His car also went into her name. We also know he was not remembering things at all; his meds, whether he had eaten, but there is no doctor diagnosis of him being incompetent. We are his other children questioning this. We are in probate, his will says all will be divided.  I have text messages from her telling me he's having a hard time remembering. Is there any thing we can do? equally.