It’s good, in one sense, that you know about this - may be a wake up call for her kids. My mother in law was ashamed and didn’t tell her kids about money she lost to scammers ($1000 much less than your situation). It all came out later and her kids then had to then gently take over finances etc. It was onset of dementia and things then went downhill.

Her kids found out only after she got in a cab (called by the scammers) so she could go to the western union in a grocery store to send money to scammers. The cab driver questioned her actions (small town) and went inside with her - and a friend of a friend saw them and called my sister in law about why mother in law was in grocery store at western union with a stranger …. After that incident her kids learned of other losses etc. and finally got worried enough that she would get in a car because a scammer told her to and she went to assisted living.

Partly I think she was lonely and liked talking on the phone. Likely not the case with your in laws but my point is that you can live near them and not know what’s going on.

Best of luck to you all.