I think that it would be fairly normal for a parent to feel a little defensive if they thought their parenting was being criticised. Your friend might well have been waiting for you to attack her - I'm glad that you didn't.

Sounds like she IS taking this seriously, but that she too doesn't know where this is coming from (though she has a hypothesis). Sounds like she is doing the best she can, but she isn't too sure on what is best in this situation. It IS possible that she picked up the behaviour from TV or something like that. So it is important not to go jumping to conclusions about who might be abusing her. That being said her behaviour is suggestive.

Three might be a little young... But I guess her mother could try asking her (in a non-leading way) where she picked up that behaviour. Though if she doesn't do that around her mother then that might be harder...

Another option would be to take her to a NON LEADING child psychologist or something like that. To teach her that the behaviour isn't appropriate, and maybe to help figure out where the behaviour is coming from.